Add wxGCD() helper function.

It is needed in wxMSW code and it looks like it could be useful to the library
users, so make it public.

See #16254.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@77019 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/math.h

@@ -165,5 +165,7 @@ inline double wxRadToDeg(double rad) { return (rad * 180.0) / M_PI; }
 #endif
 #endif /* wxUSE_APPLE_IEEE */
 
+/* Compute the greatest common divisor of two positive integers */
+WXDLLIMPEXP_BASE unsigned int wxGCD(unsigned int u, unsigned int v);
 
 #endif /* _WX_MATH_H_ */