- SDL_video.c (SDL_ShowMessageBox): replace messageboxdata, set title
or message field to "" if either of them is NULL.
- SDL_video.c (SDL_ShowSimpleMessageBox): set title or message to ""
if either of them is NULL for EMSCRIPTEN builds.
- SDL_bmessagebox.cc: add empty string check along with NULL check for
title and message fields.
- SDL_windowsmessagebox.c (AddDialogString): remove NULL string check
- SDL_windowsmessagebox.c (AddDialogControl): add empty string check
along with the NULL check.
- SDL_x11messagebox.c: revert commit 677c4cd68069
- SDL_os2messagebox.c: revert commit 2c2a489d76e7
- test/testmessage.c: Add NULL title and NULL message tests.
Add a minimal my_gradd.h containing structures and constants only used
by SDL_os2vman.c -- based on public knowledge from around the internet
including pages from http://www.osfree.org and http://www.edm2.com .
- video: VideoBootStrap->available() is gone.
- thread: all important SDL_CreateThread internal data now put into
struct SDL_Thread: changes to SDL_SYS_CreateThread().
- events / video: SDL_SetDoubleClickTime() removed -- functionality
moved to SDL_mouse.c:SDL_MouseDoubleClickTimeChanged().
- video: struct SDL_VideoDevice-> CreateWindow and CreateWindowFrom
members renamed to CreateSDLWindow and CreateSDLWindowFrom
