PSP: Add locale support

(cherry picked from commit f39c5cf989)

CMakeLists.txt

@@ -2665,6 +2665,11 @@ elseif(PSP)
     list(APPEND SOURCE_FILES ${PSP_THREAD_SOURCES})
     set(HAVE_SDL_THREADS TRUE)
   endif()
+  if(SDL_LOCALE)
+    file(GLOB PSP_LOCALE_SOURCES ${SDL2_SOURCE_DIR}/src/locale/psp/*.c)
+    list(APPEND SOURCE_FILES ${PSP_LOCALE_SOURCES})
+    set(HAVE_SDL_LOCALE TRUE)
+  endif()
   if(SDL_TIMERS)
     set(SDL_TIMER_PSP 1)
     file(GLOB PSP_TIMER_SOURCES ${SDL2_SOURCE_DIR}/src/timer/psp/*.c)