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, 1 insertions, 1 deletions

diff --git a/ext/-test-/bignum/mul.c b/ext/-test-/bignum/mul.c
index b922f34437..1b6eb911bd 100644
--- a/ext/-test-/bignum/mul.c
+++ b/ext/-test-/bignum/mul.c
@@ -1,4 +1,4 @@
-#include "internal.h"
+#include "internal/bignum.h"
 
 static VALUE
 big(VALUE x)