Change octal char literals to hex char literals

This should not change anything at all within the compiled library, but it does make the header file easier to read for non-C programmers who don't expect an octal value.

include/SDL_keycode.h

@@ -52,7 +52,7 @@ typedef enum
     SDLK_UNKNOWN = 0,
 
     SDLK_RETURN = '\r',
-    SDLK_ESCAPE = '\033',
+    SDLK_ESCAPE = '\x1B',
     SDLK_BACKSPACE = '\b',
     SDLK_TAB = '\t',
     SDLK_SPACE = ' ',
@@ -147,7 +147,7 @@ typedef enum
     SDLK_INSERT = SDL_SCANCODE_TO_KEYCODE(SDL_SCANCODE_INSERT),
     SDLK_HOME = SDL_SCANCODE_TO_KEYCODE(SDL_SCANCODE_HOME),
     SDLK_PAGEUP = SDL_SCANCODE_TO_KEYCODE(SDL_SCANCODE_PAGEUP),
-    SDLK_DELETE = '\177',
+    SDLK_DELETE = '\x1F',
     SDLK_END = SDL_SCANCODE_TO_KEYCODE(SDL_SCANCODE_END),
     SDLK_PAGEDOWN = SDL_SCANCODE_TO_KEYCODE(SDL_SCANCODE_PAGEDOWN),
     SDLK_RIGHT = SDL_SCANCODE_TO_KEYCODE(SDL_SCANCODE_RIGHT),