fix aix build error with math.h in gcc/sreal.c

[Michael Haubenwallner]

Recent commit 218765 adding sreal::to_double() breaks on AIX due to math.h
being included before _LARGE_FILES and __STDC_FORMAT_MACROS being defined
later in config.h and system.h, respectively.

2014-12-16  Michael Haubenwallner <michael.haubenwall...@ssi-schaefer.com>

        Both config.h and system.h define ABI/API macros for system headers.
        * sreal.c: Include math.h later.

Thanks!
/haubi/

Index: gcc/sreal.c
===================================================================
--- gcc/sreal.c	(revision 218780)
+++ gcc/sreal.c	(working copy)
@@ -47,9 +47,9 @@
 	sig == 0 && exp == -SREAL_MAX_EXP
 */
 
-#include <math.h>
 #include "config.h"
 #include "system.h"
+#include <math.h>
 #include "coretypes.h"
 #include "sreal.h"