Fix support for rb_file_const and rb_curses_define_const

Constant definitions using these functions have been supported, but
since RDoc::Parser::C#gen_const_table did not consider other than
`rb_define_const` the documents for them have not been found, without
`Document-const` direvtive.

Fixes ruby#1067

lib/rdoc/parser/c.rb

@@ -756,17 +756,27 @@ def find_class_comment class_name, class_mod
   def gen_const_table file_content
     table = {}
     @content.scan(%r{
-      ((?>^\s*/\*.*?\*/\s+))
-        rb_define_(\w+)\((?:\s*(?:\w+),)?\s*
-                           "(\w+)"\s*,
+      (?<doc>(?>^\s*/\*.*?\*/\s+))
+        rb_define_(?<type>\w+)\(\s*(?:\w+),\s*
+                           "(?<name>\w+)"\s*,
                            .*?\)\s*;
+    |  (?<doc>(?>^\s*/\*.*?\*/\s+))
+        rb_file_(?<type>const)\(\s*
+                           "(?<name>\w+)"\s*,
+                           .*?\)\s*;
+    |  (?<doc>(?>^\s*/\*.*?\*/\s+))
+        rb_curses_define_(?<type>const)\(\s*
+                           (?<name>\w+)
+                           \s*\)\s*;
     | Document-(?:const|global|variable):\s
-        ((?:\w+::)*\w+)
-        \s*?\n((?>.*?\*/))
+        (?<name>(?:\w+::)*\w+)
+        \s*?\n(?<doc>(?>.*?\*/))
     }mxi) do
-      case
-      when $1 then table[[$2, $3]] = $1
-      when $4 then table[$4] = "/*\n" + $5
+      name, doc, type = $~.values_at(:name, :doc, :type)
+      if type
+        table[[type, name]] = doc
+      else
+        table[name] = "/*\n" + doc
       end
     end
     table

test/rdoc/test_rdoc_parser_c.rb

@@ -583,8 +583,6 @@ def test_do_constants_curses
   mCurses = rb_define_module("Curses");
 
   /*
-   * Document-const: Curses::COLOR_BLACK
-   *
    * Value of the color black
    */
   rb_curses_define_const(COLOR_BLACK);
@@ -609,8 +607,7 @@ def test_do_constants_curses
   def test_do_constants_file
     content = <<-EOF
 void Init_File(void) {
-  /*  Document-const: LOCK_SH
-   *
+  /*
    *  Shared lock
    */
   rb_file_const("LOCK_SH", INT2FIX(LOCK_SH));