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().

build-scripts/windows-buildbot-zipper.bat

@@ -0,0 +1,31 @@
+@echo off
+rem just a helper batch file for collecting up files and zipping them.
+rem usage: windows-buildbot-zipper.bat <zipfilename>
+rem must be run from root of SDL source tree.
+
+IF EXIST VisualC\Win32\Release GOTO okaydir
+echo Please run from root of source tree after doing a Release build.
+GOTO done
+
+:okaydir
+erase /q /f /s zipper
+IF EXIST zipper GOTO zippermade
+mkdir zipper
+:zippermade
+cd zipper
+mkdir SDL
+cd SDL
+mkdir include
+mkdir lib
+mkdir lib\win32
+copy ..\..\include\*.h include\
+copy ..\..\VisualC\Win32\Release\SDL2.dll lib\win32\
+copy ..\..\VisualC\Win32\Release\SDL2.lib lib\win32\
+copy ..\..\VisualC\Win32\Release\SDL2main.lib lib\win32\
+cd ..
+zip -9r ..\%1 SDL
+cd ..
+erase /q /f /s zipper
+
+:done
+