RDoc::Parser::C: Integrate do_classes and do_modules by one regexp match

The full scan of the C source code (`@content.scan`) is very slow.
The old code invokes the scan six times in `do_classes` and
`do_modules`.

This change integrates the six scans into one by merging the regexps.
The integrated regexp is a bit hard to maintain, but the speed up is
significant: approx. 30 sec -> 20 sec in Ruby's `make rdoc`.

In addition, this change omits `do_boot_defclass` unless the file name
is `class.c`.  `boot_defclass` is too specific to Ruby's source code, so
RDoc should handle it as a special case.

Before this change:

     TOTAL    (pct)     SAMPLES    (pct)     FRAME
       858  (13.6%)         858  (13.6%)     (garbage collection)
       292   (4.6%)         264   (4.2%)     RDoc::Parser::C#do_define_class
       263   (4.2%)         250   (3.9%)     RDoc::Parser::C#do_define_module
       275   (4.3%)         241   (3.8%)     RDoc::Parser::C#do_define_class_under
       248   (3.9%)         237   (3.7%)     RDoc::Parser::C#do_define_module_under
       234   (3.7%)         234   (3.7%)     RDoc::Parser::C#gen_body_table
       219   (3.5%)         219   (3.5%)     Ripper::Lexer#state_obj
       217   (3.4%)         216   (3.4%)     RDoc::Parser::C#do_struct_define_without_accessor
       205   (3.2%)         205   (3.2%)     RDoc::Parser::C#do_boot_defclass
       205   (3.2%)         205   (3.2%)     RDoc::Parser::C#do_singleton_class

The six methods take approx. 22.2%.
`do_define_class` (4.2%) + `do_define_class_under` (3.8%) +
`do_define_module` (3,9$) + `do_define_module_under` (3.7%) +
`do_struct_define_without_accessor` (3.4%) + `do_singleton_class` (3.2%)

After this change, the methods are integrated to `do_classes_and_modules`
which takes only 5.8%.

     TOTAL    (pct)     SAMPLES    (pct)     FRAME
       812  (16.7%)         812  (16.7%)     (garbage collection)
       355   (7.3%)         284   (5.8%)     RDoc::Parser::C#do_classes_and_modules
       225   (4.6%)         225   (4.6%)     RDoc::Parser::C#gen_body_table
       429   (8.8%)         210   (4.3%)     RDoc::Parser::RubyTools#get_tk
       208   (4.3%)         208   (4.3%)     RDoc::TokenStream#add_tokens

1 files changed, 3 insertions, 31 deletions

diff --git a/test/rdoc/test_rdoc_parser_c.rb b/test/rdoc/test_rdoc_parser_c.rb
index 81727ad759..6601d28f60 100644
--- a/test/rdoc/test_rdoc_parser_c.rb
+++ b/test/rdoc/test_rdoc_parser_c.rb
@@ -304,32 +304,6 @@ void Init_Blah(void) {
     assert_equal 'This should show up as an alias', methods.last.comment.text
   end
 
-  def test_do_classes_boot_class
-    content = <<-EOF
-/* Document-class: Foo
- * this is the Foo boot class
- */
-VALUE cFoo = boot_defclass("Foo", rb_cObject);
-    EOF
-
-    klass = util_get_class content, 'cFoo'
-    assert_equal "this is the Foo boot class", klass.comment.text
-    assert_equal 'Object', klass.superclass
-  end
-
-  def test_do_classes_boot_class_nil
-    content = <<-EOF
-/* Document-class: Foo
- * this is the Foo boot class
- */
-VALUE cFoo = boot_defclass("Foo", 0);
-    EOF
-
-    klass = util_get_class content, 'cFoo'
-    assert_equal "this is the Foo boot class", klass.comment.text
-    assert_nil klass.superclass
-  end
-
   def test_do_aliases_missing_class
     content = <<-EOF
 void Init_Blah(void) {
@@ -511,7 +485,7 @@ void Init_foo(){
 
     @parser = util_parser content
 
-    @parser.do_classes
+    @parser.do_classes_and_modules
     @parser.do_constants
 
     klass = @parser.classes['cFoo']
@@ -581,8 +555,7 @@ void Init_curses(){
 
     @parser = util_parser content
 
-    @parser.do_modules
-    @parser.do_classes
+    @parser.do_classes_and_modules
     @parser.do_constants
 
     klass = @parser.classes['mCurses']
@@ -608,8 +581,7 @@ void Init_File(void) {
 
     @parser = util_parser content
 
-    @parser.do_modules
-    @parser.do_classes
+    @parser.do_classes_and_modules
     @parser.do_constants
 
     klass = @parser.classes['rb_mFConst']