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().

test/testnativecocoa.m

@@ -0,0 +1,51 @@
+
+#include "testnative.h"
+
+#ifdef TEST_NATIVE_COCOA
+
+#include <Cocoa/Cocoa.h>
+
+static void *CreateWindowCocoa(int w, int h);
+static void DestroyWindowCocoa(void *window);
+
+NativeWindowFactory CocoaWindowFactory = {
+    "cocoa",
+    CreateWindowCocoa,
+    DestroyWindowCocoa
+};
+
+static void *CreateWindowCocoa(int w, int h)
+{
+    NSAutoreleasePool *pool;
+    NSWindow *nswindow;
+    NSRect rect;
+    unsigned int style;
+
+    pool = [[NSAutoreleasePool alloc] init];
+
+    rect.origin.x = 0;
+    rect.origin.y = 0;
+    rect.size.width = w;
+    rect.size.height = h;
+    rect.origin.y = CGDisplayPixelsHigh(kCGDirectMainDisplay) - rect.origin.y - rect.size.height;
+
+    style = (NSTitledWindowMask|NSClosableWindowMask|NSMiniaturizableWindowMask);
+
+    nswindow = [[NSWindow alloc] initWithContentRect:rect styleMask:style backing:NSBackingStoreBuffered defer:FALSE];
+    [nswindow makeKeyAndOrderFront:nil];
+
+    [pool release];
+
+    return nswindow;
+}
+
+static void DestroyWindowCocoa(void *window)
+{
+    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
+    NSWindow *nswindow = (NSWindow *)window;
+
+    [nswindow close];
+    [pool release];
+}
+
+#endif