always print error backtrace

[nolta]

When an error happens in the repl you get a full backtrace:

$ julia -q -L program.j
julia> test()
type CompositeKind has no field __pl_style_func
 in set at subgrid.j:690
 in page_compose at program.j:1207
 in show at program.j:1220
 in test at program.j:1441

But when evaluating a cmdline expr, you don't:

$ julia -q -L program.j -e "test()"
type CompositeKind has no field __pl_style_func

I'm not sure if this patch is the right approach, but it passes the test suite, and appears to do the right thing:

$ julia -q -L program.j -e "test()"
type CompositeKind has no field __pl_style_func
 in set at subgrid.j:690
 in page_compose at program.j:1207
 in show at program.j:1220
 in test at program.j:1441
 in process_options at /Users/nolta/julia/j/client.j:131
 in _start at /Users/nolta/julia/j/client.j:201

[ViralBShah]

Seems like a good idea to me. Will let Jeff decide if this is the right way to address this though.

[JeffBezanson]

I will fix this a different way, since this approach doesn't give backtraces in some other cases during loading.