autotools, cmake: tighten Xfixes check && explicitly test BarrierEventID

Apparently the older versions of libXi doesn't have it.  Fixes the build
break issue reported at:
https://github.com/libsdl-org/SDL/commit/4b42c05ba1eaaaa9a4ef803acea8f13402271039#commitcomment-61427659

cmake/sdlchecks.cmake

@@ -418,7 +418,7 @@ macro(CheckX11)
     check_include_file(X11/extensions/Xinerama.h HAVE_XINERAMA_H)
     check_include_file(X11/extensions/XInput2.h HAVE_XINPUT2_H)
     check_include_file(X11/extensions/Xrandr.h HAVE_XRANDR_H)
-    check_include_file(X11/extensions/Xfixes.h HAVE_XFIXES_H)
+    check_include_file(X11/extensions/Xfixes.h HAVE_XFIXES_H_)
     check_include_file(X11/extensions/Xrender.h HAVE_XRENDER_H)
     check_include_file(X11/extensions/scrnsaver.h HAVE_XSS_H)
     check_include_file(X11/extensions/shape.h HAVE_XSHAPE_H)
@@ -538,6 +538,15 @@ macro(CheckX11)
       endif()
 
       # check along with XInput2.h because we use Xfixes with XIBarrierReleasePointer
+      if(SDL_X11_XFIXES AND HAVE_XFIXES_H_ AND HAVE_XINPUT2_H)
+        check_c_source_compiles("
+            #include <X11/Xlib.h>
+            #include <X11/Xproto.h>
+            #include <X11/extensions/XInput2.h>
+            #include <X11/extensions/Xfixes.h>
+            BarrierEventID b;
+            int main(void) { }" HAVE_XFIXES_H)
+      endif()
       if(SDL_X11_XFIXES AND HAVE_XFIXES_H AND HAVE_XINPUT2_H)
         if(HAVE_X11_SHARED AND XFIXES_LIB)
           set(SDL_VIDEO_DRIVER_X11_DYNAMIC_XFIXES "\"${XFIXES_LIB_SONAME}\"")

configure

@@ -22123,17 +22123,31 @@ fi
             if test x$enable_video_x11_xfixes = xyes; then
                 definitely_enable_video_x11_xfixes=no
                 # check along with XInput2.h because we use Xfixes with XIBarrierReleasePointer
-                ac_fn_c_check_header_compile "$LINENO" "X11/extensions/Xfixes.h" "ac_cv_header_X11_extensions_Xfixes_h" "#include <X11/Xlib.h>
-                                 #include <X11/Xproto.h>
-                                 #include <X11/extensions/XInput2.h>
-"
-if test "x$ac_cv_header_X11_extensions_Xfixes_h" = xyes; then :
+                { $as_echo "$as_me:${as_lineno-$LINENO}: checking for X11/extensions/Xfixes.h" >&5
+$as_echo_n "checking for X11/extensions/Xfixes.h... " >&6; }
+                cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+                    #include <X11/Xlib.h>
+                    #include <X11/Xproto.h>
+                    #include <X11/extensions/XInput2.h>
+                    #include <X11/extensions/Xfixes.h>
+int
+main ()
+{
+BarrierEventID b;
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
   have_xfixes_h_hdr=yes
 else
   have_xfixes_h_hdr=no
 fi
-
-
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+                { $as_echo "$as_me:${as_lineno-$LINENO}: result: $have_xfixes_h_hdr" >&5
+$as_echo "$have_xfixes_h_hdr" >&6; }
                 if test x$have_xfixes_h_hdr = xyes; then
                     if test x$enable_x11_shared = xyes && test x$xfixes_lib != x ; then
                         echo "-- dynamic libXfixes -> $xfixes_lib"

configure.ac

@@ -1973,12 +1973,16 @@ XITouchClassInfo *t;
             if test x$enable_video_x11_xfixes = xyes; then
                 definitely_enable_video_x11_xfixes=no
                 # check along with XInput2.h because we use Xfixes with XIBarrierReleasePointer
-                AC_CHECK_HEADER(X11/extensions/Xfixes.h,
-                                have_xfixes_h_hdr=yes,
-                                have_xfixes_h_hdr=no,
-                                [#include <X11/Xlib.h>
-                                 #include <X11/Xproto.h>
-                                 #include <X11/extensions/XInput2.h>])
+                AC_MSG_CHECKING(for X11/extensions/Xfixes.h)
+                AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
+                    #include <X11/Xlib.h>
+                    #include <X11/Xproto.h>
+                    #include <X11/extensions/XInput2.h>
+                    #include <X11/extensions/Xfixes.h>]],
+                    [BarrierEventID b;])],
+                    [have_xfixes_h_hdr=yes],
+                    [have_xfixes_h_hdr=no])
+                AC_MSG_RESULT($have_xfixes_h_hdr)
                 if test x$have_xfixes_h_hdr = xyes; then
                     if test x$enable_x11_shared = xyes && test x$xfixes_lib != x ; then
                         echo "-- dynamic libXfixes -> $xfixes_lib"

src/video/x11/SDL_x11sym.h

@@ -163,7 +163,7 @@ SDL_X11_SYM(Status,XmbTextListToTextProperty,(Display* a,char** b,int c,XICCEnco
 SDL_X11_MODULE(XFIXES)
 SDL_X11_SYM(PointerBarrier, XFixesCreatePointerBarrier, (Display* a, Window b, int c, int d, int e, int f, int g, int h, int *i),(a,b,c,d,e,f,g,h,i),return)
 SDL_X11_SYM(void, XFixesDestroyPointerBarrier, (Display* a, PointerBarrier b), (a,b),)
-SDL_X11_SYM(int, XIBarrierReleasePointer,(Display* a,  int b, PointerBarrier c, BarrierEventID d), (a,b,c,d), return)
+SDL_X11_SYM(int, XIBarrierReleasePointer,(Display* a,  int b, PointerBarrier c, BarrierEventID d), (a,b,c,d), return) /* this is actually Xinput2 */
 SDL_X11_SYM(Status, XFixesQueryVersion,(Display* a, int* b, int* c), (a,b,c), return)
 #endif