control sequence improperly handled when split across reads

[dankamongmen]

Work on #2435 led to a 4095B input event followed by 3192B. we had a control sequence split across the two reads:

process_escape:1849:initialized automaton to 1                                                                                      
process_escape:1861:walk result on 93 (]): 0 404                                                                                    
process_escape:1861:walk result on 52 (4): 0 405                                                                                    
process_escape:1861:walk result on 59 (;): 0 406                                                                                    
process_melange:2035:input 4092/3 [0x5d] (])                                                                                        
process_melange:2035:input 4093/2 [0x34] (4)                                                                                        
process_melange:2035:input 4094/1 [0x3b] (;)                                                                                        
block_on_input:2115:blocking on input availability                                                                                  
block_on_input:2172:waiting on 1 fds (ibuf: 0/8192)                                                                                 
block_on_input:2199:poll returned 1                                                                                                 
block_on_input:2213:got events: tI                                                                                                  
read_input_nblock:1811:read 3192B from 0 (5000B left)                                                                               
process_melange:2035:input 0/3192 [0x31] (1)                                                                                        
process_melange:2035:input 1/3191 [0x34] (4)                                                                                        
process_melange:2035:input 2/3190 [0x37] (7)                                                                                        
process_melange:2035:input 3/3189 [0x3b] (;)                                                                                        
process_melange:2035:input 4/3188 [0x72] (r)                                                                                        
process_melange:2035:input 5/3187 [0x67] (g)                                                                                        
process_melange:2035:input 6/3186 [0x62] (b)                                                                                        
process_melange:2035:input 7/3185 [0x3a] (:)                                                                                        
process_melange:2035:input 8/3184 [0x61] (a)                                                                                        
process_melange:2035:input 9/3183 [0x66] (f)                                                                                        
process_melange:2035:input 10/3182 [0x61] (a)                                                                                       
process_melange:2035:input 11/3181 [0x66] (f)                                                                                       
process_melange:2035:input 12/3180 [0x2f] (/)                                                                                       
process_melange:2035:input 13/3179 [0x61] (a)                                                                                       
process_melange:2035:input 14/3178 [0x66] (f)                                                                                       
process_melange:2035:input 15/3177 [0x61] (a)                                                                                       
process_melange:2035:input 16/3176 [0x66] (f)                                                                                       
process_melange:2035:input 17/3175 [0x2f] (/)                                                                                       
process_melange:2035:input 18/3174 [0x66] (f)                                                                                       
process_melange:2035:input 19/3173 [0x66] (f)                                                                                       
process_melange:2035:input 20/3172 [0x66] (f)                                                                                       
process_melange:2035:input 21/3171 [0x66] (f)                                                                                       
process_melange:2035:input 22/3170 [0x1b] ( )                                                                                       
process_escape:1861:walk result on 52 (4): 0 407                                                                                    
process_escape:1861:walk result on 59 (;): 0 408                                                                                    
walk_automaton:559:unexpected transition on 408[49]                                                                                 
process_escape:1861:walk result on 49 (1): -1 0                                                                                     
process_melange:2035:input 23/3169 [0x5c] (\)                                                                                       
process_melange:2035:input 24/3168 [0x1b] ( )                                                                                       
process_escape:1849:initialized automaton to 1        

as you can see, it wasn't properly combined, and we ended up (a) losing the sequence and (b) echoing it to output.

[dankamongmen]

we're heading directly into process_melange() at the end. we ought be leaving that open.

[dankamongmen]

we're clearing ictx->midescape, and shouldn't be.

[dankamongmen]

ok, this is handled in dankamongmen/getpalette.