Do not redefine math functions for floats if compiler complies with C99 or POSIX.1-2001

This is useful for gcc which does not define sqrtf/powf/... functions with preprocessor and therefore always used sqrt/pow/...
Float functions are generally 20-50% faster than their equivalents for double type.

source/blender/blenlib/BLI_math_base.h

@@ -80,6 +80,9 @@
 #define MAXFLOAT  ((float)3.40282347e+38)
 #endif
 
+/* do not redefine functions from C99 or POSIX.1-2001 */
+#if !(defined(_ISOC99_SOURCE) || _POSIX_C_SOURCE >= 200112L)
+
 #ifndef sqrtf
 #define sqrtf(a) ((float)sqrt(a))
 #endif
@@ -129,6 +132,8 @@
 #define hypotf(a, b) ((float)hypot(a, b))
 #endif
 
+#endif
+
 #ifdef WIN32
 #  ifndef FREE_WINDOWS
 #    define isnan(n) _isnan(n)