winex11.drv: Avoid conflicting definitions of WINGDIAPI.

[Dmitry Timoshkov]

This patch fixes a warning like:

In file included from x11drv.h:57,
                 from opengl.c:48:
../../include/wingdi.h:30:1: warning: "WINGDIAPI" redefined
In file included from opengl.c:40:
/usr/include/GL/gl.h:39:1: warning: this is the location of the previous definition
---
 dlls/winex11.drv/opengl.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/dlls/winex11.drv/opengl.c b/dlls/winex11.drv/opengl.c
index f43127c..44882cb 100644
--- a/dlls/winex11.drv/opengl.c
+++ b/dlls/winex11.drv/opengl.c
@@ -44,6 +44,7 @@
 #endif
 #undef APIENTRY
 #undef GLAPI
+#undef WINGDIAPI
 
 #include "x11drv.h"
 #include "winternl.h"
-- 
1.7.11.1