decouple internal.h headers

Saves comitters' daily life by avoid #include-ing everything from
internal.h to make each file do so instead.  This would significantly
speed up incremental builds.

We take the following inclusion order in this changeset:

1.  "ruby/config.h", where _GNU_SOURCE is defined (must be the very
    first thing among everything).
2.  RUBY_EXTCONF_H if any.
3.  Standard C headers, sorted alphabetically.
4.  Other system headers, maybe guarded by #ifdef
5.  Everything else, sorted alphabetically.

Exceptions are those win32-related headers, which tend not be self-
containing (headers have inclusion order dependencies).

1 files changed, 3 insertions, 1 deletions

diff --git a/ext/coverage/coverage.c b/ext/coverage/coverage.c
index 8503c9d6c6..34b0849fc4 100644
--- a/ext/coverage/coverage.c
+++ b/ext/coverage/coverage.c
@@ -8,9 +8,11 @@
 
 ************************************************/
 
+#include "gc.h"
+#include "internal/hash.h"
+#include "internal/thread.h"
 #include "ruby.h"
 #include "vm_core.h"
-#include "gc.h"
 
 static int current_mode;
 static VALUE me2counter = Qnil;