ruby/missing.h: M_PI fallback definition

* include/ruby/missing.h (M_PI, M_PI_2): fallback definitions for
  VC6.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51313 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

complex.c

@@ -5,12 +5,12 @@
   which is written in ruby.
 */
 
-#include "internal.h"
 #if defined _MSC_VER
 /* Microsoft Visual C does not define M_PI and others by default */
 # define _USE_MATH_DEFINES 1
 #endif
 #include <math.h>
+#include "internal.h"
 
 #define NDEBUG
 #include <assert.h>

include/ruby/missing.h

@@ -37,6 +37,13 @@ extern "C" {
 #endif
 #endif
 
+#ifndef M_PI
+# define M_PI 3.14159265358979323846
+#endif
+#ifndef M_PI_2
+# define M_PI_2 (M_PI/2)
+#endif
+
 #ifndef RUBY_SYMBOL_EXPORT_BEGIN
 # define RUBY_SYMBOL_EXPORT_BEGIN /* begin */
 # define RUBY_SYMBOL_EXPORT_END   /* end */

math.c

@@ -106,9 +106,6 @@ num2dbl_with_to_f(VALUE num)
 static VALUE
 math_atan2(VALUE obj, VALUE y, VALUE x)
 {
-#ifndef M_PI
-# define M_PI 3.14159265358979323846
-#endif
     double dx, dy;
     dx = Get_Double(x);
     dy = Get_Double(y);