all: merge .m files with their .go counterparts

The only reason for separate files is Objective-C callbacks into Go,
or when the Go side is common, yet the Objective-C side differs from
macOS to iOS.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

gpu/headless/headless_macos.m

@@ -10,10 +10,6 @@
 #include <CoreFoundation/CoreFoundation.h>
 #include "_cgo_export.h"
 
-void gio_headless_releaseContext(CFTypeRef ctxRef) {
-	CFBridgingRelease(ctxRef);
-}
-
 CFTypeRef gio_headless_newContext(void) {
 	NSOpenGLPixelFormatAttribute attr[] = {
 		NSOpenGLPFAOpenGLProfile, NSOpenGLProfileVersion3_2Core,