Remove MicroWindows support.

MicroWindows (aka Nano-X) support hasn’t been updated since 2010 and last work for it in wxWidgets happened more than 10 years ago.

include/wx/defs.h

@@ -530,7 +530,7 @@ typedef short int WXTYPE;
 
 /*  wxCALLBACK should be used for the functions which are called back by */
 /*  Windows (such as compare function for wxListCtrl) */
-#if defined(__WIN32__) && !defined(__WXMICROWIN__)
+#if defined(__WIN32__)
     #define wxCALLBACK wxSTDCALL
 #else
     /*  no stdcall under Unix nor Win16 */
@@ -1140,7 +1140,6 @@ typedef wxUint32 wxDword;
 #elif (defined(SIZEOF_LONG_LONG) && SIZEOF_LONG_LONG >= 8)  || \
         defined(__GNUC__) || \
         defined(__CYGWIN__) || \
-        defined(__WXMICROWIN__) || \
         (defined(__DJGPP__) && __DJGPP__ >= 2)
     #define wxLongLong_t long long
     #define wxLongLongSuffix ll
@@ -3224,7 +3223,7 @@ typedef wxW64 long         WXLPARAM;
 typedef wxW64 long         WXLRESULT;
 #endif
 
-#if defined(__GNUWIN32__) || defined(__WXMICROWIN__)
+#if defined(__GNUWIN32__)
 typedef int             (*WXFARPROC)();
 #else
 typedef int             (__stdcall *WXFARPROC)();