[Freeciv-Dev] (PR#8785) autoconf check for WIN32_NATIVE isn't good

["Jason Short" <jdorje@xxxxxxxxxxxxxxxxxxxxx>]

<URL: http://rt.freeciv.org/Ticket/Display.html?id=8785 >

The current autoconf check for WIN32_NATIVE just checks if the compiler 
is mingw.  This is bad because it won't work with any other compilers. 
(Honestly I don't know what other problems one might run into with a 
different compiler.  I'm not likely to ever try myself.)

However it should be easy enough to fix.  Andi has already explained how 
(if not why) AC_CHECK_FUNCS won't work with win32-native functions. 
However it should be easy enough to write a test that tries to compile a 
specially tailored program, and sets WIN32_NATIVE accordingly.

jason