Move our own CFM_BACKCOLOR definition to src/msw/textctrl.cpp

It is only needed/used in this source file, no need to have it in the global
header.

include/wx/msw/missing.h

@@ -220,10 +220,6 @@
     #define TB_SETDISABLEDIMAGELIST (WM_USER + 54)
 #endif // !defined(TB_SETDISABLEDIMAGELIST)
 
-#ifndef CFM_BACKCOLOR
-    #define CFM_BACKCOLOR 0x04000000
-#endif
-
 #ifndef HANGUL_CHARSET
     #define HANGUL_CHARSET 129
 #endif

src/msw/textctrl.cpp

@@ -72,6 +72,10 @@
 
 #include "wx/msw/missing.h"
 
+#ifndef CFM_BACKCOLOR
+    #define CFM_BACKCOLOR 0x04000000
+#endif
+
 #if wxUSE_DRAG_AND_DROP && wxUSE_RICHEDIT
 
 // dummy value used for m_dropTarget, different from any valid pointer value