Fixed crash if initialization of EGL failed but was tried again later.

The internal function SDL_EGL_LoadLibrary() did not delete and remove a mostly
uninitialized data structure if loading the library first failed. A later try to
use EGL then skipped initialization and assumed it was previously successful
because the data structure now already existed. This led to at least one crash
in the internal function SDL_EGL_ChooseConfig() because a NULL pointer was
dereferenced to make a call to eglBindAPI().

README-SDL.txt

@@ -0,0 +1,13 @@
+
+Please distribute this file with the SDL runtime environment:
+
+The Simple DirectMedia Layer (SDL for short) is a cross-platform library
+designed to make it easy to write multi-media software, such as games and
+emulators.
+
+The Simple DirectMedia Layer library source code is available from:
+http://www.libsdl.org/
+
+This library is distributed under the terms of the zlib license:
+http://www.zlib.net/zlib_license.html
+