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, 12 insertions, 4 deletions

diff --git a/complex.c b/complex.c
index cdd5edc50a..bce22be735 100644
--- a/complex.c
+++ b/complex.c
@@ -6,15 +6,25 @@
 */
 
 #include "ruby/config.h"
+
 #if defined _MSC_VER
 /* Microsoft Visual C does not define M_PI and others by default */
 # define _USE_MATH_DEFINES 1
 #endif
+
+#include <ctype.h>
 #include <math.h>
-#include "internal.h"
-#include "id.h"
 
 #define NDEBUG
+#include "id.h"
+#include "internal.h"
+#include "internal/class.h"
+#include "internal/complex.h"
+#include "internal/error.h"
+#include "internal/math.h"
+#include "internal/numeric.h"
+#include "internal/object.h"
+#include "internal/rational.h"
 #include "ruby_assert.h"
 
 #define ZERO INT2FIX(0)
@@ -1700,8 +1710,6 @@ numeric_to_c(VALUE self)
     return rb_complex_new1(self);
 }
 
-#include <ctype.h>
-
 inline static int
 issign(int c)
 {