Make EGL loading more resilient.

Lesson learned while trying to run L4D2 under Wayland :)
Mac: Trigger SDL_FINGERUP for all touches.

Fixes bug #2348. Thanks to Alex Szpakowski for the patch!
Adds README-dynapi.txt based on Ryan's G+ post (lightly edited)

Original post: https://plus.google.com/103391075724026391227/posts/TB8UfnDYu4U
Tests: Refactor key modifier checking.
Test: Add Shift-Enter to switch between FS and desktop FS.
Allow switching between FS and desktop FS.

This should fix bug #2057 (https://bugzilla.libsdl.org/show_bug.cgi?id=2057)
Mac: Don't give windows focus back when we're closing them.

Fixes bug #1840 (https://bugzilla.libsdl.org/show_bug.cgi?id=1840)
Don't minimize fullscreen windows when destroying them.

Previously, we'd minimize fullscreen windows (if
SDL_HINT_VIDEO_MINIMIZE_ON_FOCUS_LOSS was set) during SDL_DestroyWindow if they
had keyboard focus, because we call SDL_SetKeyboardFocus(NULL) which yields a
OnWindowsFocusLost event.

Related to https://bugzilla.libsdl.org/show_bug.cgi?id=1840
Fix to compile against the Wayland v1.4 headers
Fixes prototype declaration for wl_proxy_marshal_constructor [Wayland 1.4]
Make sure you clean up the associated renderer when destroying a window.