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, 15 insertions, 8 deletions

diff --git a/rational.c b/rational.c
index c606f3c625..8b4a39452c 100644
--- a/rational.c
+++ b/rational.c
@@ -5,23 +5,32 @@
   which is written in ruby.
 */
 
-#include "internal.h"
-#include "id.h"
-#include <math.h>
+#include "ruby/config.h"
+
+#include <ctype.h>
 #include <float.h>
+#include <math.h>
 
 #ifdef HAVE_IEEEFP_H
 #include <ieeefp.h>
 #endif
 
-#define NDEBUG
-#include "ruby_assert.h"
-
 #if defined(HAVE_LIBGMP) && defined(HAVE_GMP_H)
 #define USE_GMP
 #include <gmp.h>
 #endif
 
+#define NDEBUG
+#include "id.h"
+#include "internal.h"
+#include "internal/complex.h"
+#include "internal/error.h"
+#include "internal/gc.h"
+#include "internal/numeric.h"
+#include "internal/object.h"
+#include "internal/rational.h"
+#include "ruby_assert.h"
+
 #define ZERO INT2FIX(0)
 #define ONE INT2FIX(1)
 #define TWO INT2FIX(2)
@@ -2299,8 +2308,6 @@ float_rationalize(int argc, VALUE *argv, VALUE self)
     }
 }
 
-#include <ctype.h>
-
 inline static int
 issign(int c)
 {