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, 2 insertions, 0 deletions

diff --git a/constant.h b/constant.h
index 610bdf1dfe..1396651e21 100644
--- a/constant.h
+++ b/constant.h
@@ -10,6 +10,8 @@
 **********************************************************************/
 #ifndef CONSTANT_H
 #define CONSTANT_H
+#include "ruby/ruby.h"
+#include "id_table.h"
 
 typedef enum {
     CONST_DEPRECATED = 0x100,