Fix FTBFS on RHEL 5 because SDL is not detected

This resolves Bug 2488

Signed-off-by: François Andriot <francois.andriot@free.fr>

ConfigureChecks.cmake

@@ -74,7 +74,12 @@ if( BUILD_NOATUN_PLUGINS )
   if( WITH_SDL )
     pkg_search_module( SDL sdl )
     if( NOT SDL_FOUND )
+      check_include_file( SDL/SDL.h HAVE_SDL_H )
+      if( NOT HAVE_SDL_H )
         tde_message_fatal( "SDL is requested, but was not found on your system" )
+      endif ( )
+      set ( SDL_INCLUDE_DIRS /usr/include/SDL )
+      set ( SDL_LIBRARIES SDL pthread )
     endif( )
   endif( WITH_SDL )