cocoa_gl_ctx: runtime-guard setColorSpace: for pre-10.6 Leopard

On 10.5 Leopard, RetroArch crashes during GL context creation:

    [NSWindow setColorSpace:]: unrecognized selector sent to
        instance 0x631bad0

-[NSWindow setColorSpace:] is annotated NS_AVAILABLE_MAC(10_6).
Snow Leopard introduced color-space-aware window tagging; 10.5's
NSWindow doesn't have the selector.

Same class of runtime issue as aa5c926 (setHelpMenu:) and the
URLForResource: guard: compile succeeds because messages to id
dispatch dynamically, but the Obj-C runtime can't resolve the
selector at dispatch time and throws NSInvalidArgumentException.

Runtime-guard with respondsToSelector::

    NSWindow *win = [g_view window];
    if ([win respondsToSelector:@selector(setColorSpace:)])
        [win setColorSpace:[NSColorSpace sRGBColorSpace]];

Wrapped in a block so the local NSWindow* doesn't leak into the
surrounding scope.

+[NSColorSpace sRGBColorSpace] on the same line is 10.5+
(NS_AVAILABLE_MAC(10_5) per the header) so it stays unguarded.
Only the NSWindow selector is the 10.6 addition.

Behavioral impact on Leopard: windows use the system default color
space, which is what Leopard always did anyway - color-space-aware
window tagging didn't exist pre-10.6.  Modern macOS still gets the
explicit sRGB tag as before.

Author: LibretroAdmin

gfx/drivers_context/cocoa_gl_ctx.m

@@ -438,7 +438,17 @@ static bool cocoa_gl_gfx_ctx_set_video_mode(void *data,
    }
 
    [g_ctx setView:g_view];
-   [[g_view window] setColorSpace:[NSColorSpace sRGBColorSpace]];
+   {
+      /* -[NSWindow setColorSpace:] is NS_AVAILABLE_MAC(10_6).  On 10.5
+       * Leopard the selector doesn't exist and the runtime throws
+       * "unrecognized selector".  Without this call the window simply
+       * uses the default colour space (which is what 10.5 always did
+       * anyway), so skip it on systems that lack the method.
+       * +[NSColorSpace sRGBColorSpace] itself is 10.5+ and is safe. */
+      NSWindow *win = [g_view window];
+      if ([win respondsToSelector:@selector(setColorSpace:)])
+         [win setColorSpace:[NSColorSpace sRGBColorSpace]];
+   }
 #ifdef OSX
    [g_ctx makeCurrentContext];
 #else