Reorder and add missing X11 and SDL key syms

SDL1 and SDL2 key syms have been merged.
(SDL) Add support to key binding
(Menu) Rewrite menu_action_ok shader options
Merge pull request #927 from heuripedes/keymaps

X11 and SDL Key map improvements
(Menu) Get rid of OPEN_HISTORY enum
(Menu) Get rid of hardcoded enums for video/audio softplugs
(Menu) Don't spam log
(Menu) Get rid of some unnecessary HAVE_OVERLAY ifdefs
(Menu) Cleanups
(menu_input_line_cb.c) 80-char limit cleanups
(Menu/General) Refactor rarch_defer_core
Cleanups - C-style comments, 80-char limit
(gfx/scaler) Get rid of some unnecessary ifs
Move rarch_defer_core to retroarch.c