Realign SDL's CMakeLists.txt with the cherry-picked SDL commits.

Those commits are mainly for fixing the keyboard input handling on RPI platform.

Source/ThirdParty/SDL/CMakeLists.txt

@@ -982,6 +982,7 @@ elseif(UNIX)    # Urho3D - at this point both UNIX and UNIX_SYS should be equiva
     if (UDEV_H_INCLUDE_DIRS)
       set (HAVE_LIBUDEV_H TRUE)
       include_directories (${UDEV_H_INCLUDE_DIRS})
+      # TODO: find the shared library and store the result in the SDL_UDEV_DYNAMIC variable
     endif ()
 
     # Urho3D - bug fix - dbus/dbus.h is installed under path suffix 'dbus-1.0', so the following find_path() is needed even when not cross-compiling

Source/ThirdParty/SDL/include/SDL_config.h.cmake

@@ -363,6 +363,15 @@
 #cmakedefine SDL_ASSEMBLY_ROUTINES @SDL_ASSEMBLY_ROUTINES@
 #cmakedefine SDL_ALTIVEC_BLITTERS @SDL_ALTIVEC_BLITTERS@
 
+/* Enable ime support */
+#cmakedefine SDL_USE_IME @SDL_USE_IME@
+
+/* Enable dynamic udev support */
+#cmakedefine SDL_UDEV_DYNAMIC @SDL_UDEV_DYNAMIC@
+
+/* Enable dynamic libsamplerate support */
+#cmakedefine SDL_LIBSAMPLERATE_DYNAMIC @SDL_LIBSAMPLERATE_DYNAMIC@
+
 // Urho3D - needed on iOS platform
 #cmakedefine SDL_IPHONE_KEYBOARD @SDL_IPHONE_KEYBOARD@
 #cmakedefine SDL_IPHONE_LAUNCHSCREEN @SDL_IPHONE_LAUNCHSCREEN@