Make XF86VIDMODE extension optional

Code in glx/glxcmds.c which uses the XF86VIDMODE extension is already guarded.  Also use
that guard to control inclusion of the xf86vmode.h header, and only enable that guard if the
XF86VIDMODE extension is found by pkgconfig.

This changes the behaviour on platforms which XF86VIDMODE exists, in that XF86VIDMODE used to
be mandatory, but is now optional.

Presumably other build systems are already arranging for -DXF86VIDMODE to be supplied to the
complier when glxcmds.c is compiled, so are not affected by this change

Signed-off-by: Jon TURNEY <jon.turney@dronecode.org.uk>

configs/autoconf.in

@@ -195,3 +195,5 @@ ifneq ($(LLVM_VERSION),)
   HAVE_LLVM := 0x0$(subst .,0,$(LLVM_VERSION:svn=))
   DEFINES += -DHAVE_LLVM=$(HAVE_LLVM)
 endif
+
+HAVE_XF86VIDMODE = @HAVE_XF86VIDMODE@

configure.ac

@@ -626,8 +626,15 @@ dri)
 
     # find the DRI deps for libGL
     if test "$x11_pkgconfig" = yes; then
+        dri_modules="x11 xext xdamage xfixes"
+
+        # add xf86vidmode if available
+        PKG_CHECK_MODULES([XF86VIDMODE], [xxf86vm], HAVE_XF86VIDMODE=yes, HAVE_XF86VIDMODE=no)
+        if test "$HAVE_XF86VIDMODE" = yes ; then
+            dri_modules="$dri_modules xxf86vm"
+        fi
+
         # add xcb modules if necessary
-        dri_modules="x11 xext xxf86vm xdamage xfixes"
         if test "$enable_xcb" = yes; then
             dri_modules="$dri_modules x11-xcb xcb-glx"
         fi
@@ -676,6 +683,8 @@ AC_SUBST([GLESv2_LIB_DEPS])
 AC_SUBST([GLESv2_PC_LIB_PRIV])
 
 
+AC_SUBST([HAVE_XF86VIDMODE])
+
 dnl
 dnl More X11 setup
 dnl

src/glx/Makefile

@@ -1,7 +1,11 @@
 TOP = ../..
 include $(TOP)/configs/current
 
-EXTRA_DEFINES = -DXF86VIDMODE -D_REENTRANT \
+ifeq ($(HAVE_XF86VIDMODE),yes)
+EXTRA_DEFINES_XF86VIDMODE = -DXF86VIDMODE
+endif
+
+EXTRA_DEFINES = $(EXTRA_DEFINES_XF86VIDMODE) -D_REENTRANT \
                 -DDEFAULT_DRIVER_DIR=\"$(DRI_DRIVER_SEARCH_DIR)\"
 
 SOURCES = \

src/glx/glxcmds.c

@@ -44,7 +44,9 @@
 #include "glx_error.h"
 #else
 #include <sys/time.h>
+#ifdef XF86VIDMODE
 #include <X11/extensions/xf86vmode.h>
+#endif
 #include "xf86dri.h"
 #endif
 #else