Attempt to fix the Cygwin build problem for once and for all

simgear/screen/GLBitmaps.cxx

@@ -2,8 +2,12 @@
 #  include <simgear_config.h>
 #endif
 
-#ifdef HAVE_WINDOWS_H
-#  include <windows.h>                     
+#if defined(__CYGWIN__)  /* && !defined(USING_X) */
+#define WIN32
+#endif
+
+#if defined(WIN32)  /* MINGW and MSC predefine WIN32 */
+# include <windows.h>
 #endif
 
 #include <stdio.h>

simgear/screen/extensions.hxx

@@ -24,12 +24,18 @@
 #ifndef __SG_EXTENSIONS_HXX
 #define __SG_EXTENSIONS_HXX 1
 
-#if defined(WIN32) && !defined(__CYGWIN__) && !defined(__MINGW32__)
-# include <windows.h>
-#else
+#if !defined(WIN32)
 # include <dlfcn.h>
 #endif
 
+#if defined(__CYGWIN__)  /* && !defined(USING_X) */
+#define WIN32
+#endif
+
+#if defined(WIN32)  /* MINGW and MSC predefine WIN32 */
+# include <windows.h>
+#endif
+
 #include <GL/gl.h>
 
 

simgear/screen/screen-dump.cxx

@@ -24,8 +24,12 @@
 #  include <simgear_config.h>
 #endif
 
-#ifdef HAVE_WINDOWS_H
-#  include <windows.h>                     
+#if defined(__CYGWIN__)  /* && !defined(USING_X) */
+#define WIN32
+#endif
+
+#if defined(WIN32)  /* MINGW and MSC predefine WIN32 */
+# include <windows.h>
 #endif
 
 #include <stdio.h>

simgear/xgl/xgl.c

@@ -2,10 +2,6 @@
 #  include <simgear_config.h>
 #endif
 
-#ifdef HAVE_WINDOWS_H
-#  include <windows.h>
-#endif
-
 #include "xgl.h"
 
 #ifdef USING_GLUT

simgear/xgl/xgl.h

@@ -6,8 +6,12 @@
 #  include <simgear_config.h>
 #endif
 
-#ifdef HAVE_WINDOWS_H
-#  include <windows.h>
+#if defined(__CYGWIN__)  /* && !defined(USING_X) */
+#define WIN32
+#endif
+
+#if defined(WIN32)  /* MINGW and MSC predefine WIN32 */
+# include <windows.h>
 #endif
 
 #include <GL/gl.h>