Improve workaround for MinGW math.h bug in strict ANSI mode.

Declare _hypot() function globally, predefining __NO_INLINE__ in wx/math.h is
not enough as <math.h> is also included from some other standard headers, e.g.
<algorithm>, and including them results in the same bug as in wx/math.h
(i.e. https://sourceforge.net/p/mingw/bugs/2250/).

include/wx/math.h

@@ -15,17 +15,6 @@
 
 #include "wx/defs.h"
 
-#ifdef wxNEEDS_STRICT_ANSI_WORKAROUNDS
-    /*
-        In addition to declaring _finite() ourselves below, we also must work
-        around a compilation error in MinGW standard header itself, see
-        https://sourceforge.net/p/mingw/bugs/2250/
-     */
-    #ifndef __NO_INLINE__
-        #define __NO_INLINE__
-    #endif
-#endif
-
 #include <math.h>
 
 #ifndef M_PI