include/wincon.h: Replace BOOL by WINBOOL in struct _CONSOLE_SCREEN_BUFFER_INFOEX.

Fixes BOOL conflict with GNUStep
Patch by Roland Schwingel <roland.schwingel@onevision.com>

git-svn-id: svn://svn.code.sf.net/p/mingw-w64/code/trunk@5939 4407c894-4637-0410-b4f5-ada5f102cad1