Mingw: Add -DGLEW_STATIC, assuming that everyone will use a static glew

When somebody figures out how to link to the dynamic one, this will have
to be revisited.

Makefile.am

@@ -48,7 +48,7 @@ AM_CPPFLAGS = \
   -I$(srcdir)/engine/inc \
   -I$(srcdir)/engine/sec \
   -DC4ENGINE \
-  $(GTK_CFLAGS) $(FREETYPE_CFLAGS) $(SDL_CFLAGS)
+  $(GLEW_CFLAGS) $(GTK_CFLAGS) $(FREETYPE_CFLAGS) $(SDL_CFLAGS)
 
 #various hacks to get dependency tracking working with a precompiled C4Include
 if RECENT_GCC

configure.ac

@@ -213,6 +213,7 @@ if test $with_gl = yes; then
       [AC_MSG_ERROR([glu32 not found.])])
     AC_CHECK_LIB(glew32, main, [CLONK_LIBS="-lglew32 $CLONK_LIBS"],
       [AC_MSG_ERROR([glew not found.])])
+    AC_SUBST([GLEW_CFLAGS],["-DGLEW_STATIC"])
   else
     AC_CHECK_LIB(GL, glBegin, [CLONK_LIBS="-lGL $CLONK_LIBS"],
       [AC_MSG_ERROR([libGL not found.])])