IOS7: Autorelease overloaded key arrays

There are memory leakages when returning to the ScummVM iOS
application if it has been running in background.
The reason for the memory leaks is that the system calls the
keyCommands function every time the keyboard view became the
first responder.

Since the overloaded keys are loaded into allocated arrays
each time the keyCommands function is called they are never
released. Since the keyCommands is running in an autorelease
block, make the allocation to autorelease.

This is required since we don't utilize ARC.

backends/platform/ios7/ios7_keyboard.mm

@@ -281,7 +281,7 @@ - (UIKeyCommand *)createKeyCommandForKey:(NSString *)key withModifierFlags:(UIKe
 }
 
 - (NSArray *)overloadKeys:(NSArray<NSString *> *)keys withSelector:(SEL)selector {
-	NSMutableArray<UIKeyCommand *> *overloadedKeys = [[NSMutableArray alloc] init];
+	NSMutableArray<UIKeyCommand *> *overloadedKeys = [[[NSMutableArray alloc] init] autorelease];
 	for (NSString *key in keys) {
 		[overloadedKeys addObject:[self createKeyCommandForKey:key withModifierFlags:0 andSelector:selector]];
 		[overloadedKeys addObject:[self createKeyCommandForKey:key withModifierFlags:UIKeyModifierShift andSelector:selector]];
@@ -296,13 +296,13 @@ - (NSArray *)overloadKeys:(NSArray<NSString *> *)keys withSelector:(SEL)selector
 }
 
 - (NSArray *)overloadArrowKeys {
-	NSArray<NSString *> *arrowKeys = [[NSArray alloc] initWithObjects:UIKeyInputUpArrow, UIKeyInputDownArrow, UIKeyInputLeftArrow, UIKeyInputRightArrow, nil];
+	NSArray<NSString *> *arrowKeys = [[[NSArray alloc] initWithObjects:UIKeyInputUpArrow, UIKeyInputDownArrow, UIKeyInputLeftArrow, UIKeyInputRightArrow, nil] autorelease];
 	return [self overloadKeys:arrowKeys withSelector:@selector(handleArrowKey:)];
 }
 
 - (NSArray *)overloadRomanLetters {
 	NSString *romanLetters = @"abcdefghijklmnopqrstuvwxyz";
-	NSMutableArray<NSString *> *letters = [[NSMutableArray alloc] init];
+	NSMutableArray<NSString *> *letters = [[[NSMutableArray alloc] init] autorelease];
 	for (NSUInteger x = 0; x < romanLetters.length; x++) {
 		unichar c = [romanLetters characterAtIndex:x];
 		[letters addObject:[NSString stringWithCharacters:&c length:1]];
@@ -312,7 +312,7 @@ - (NSArray *)overloadRomanLetters {
 
 - (NSArray *)overloadNumbers {
 	NSString *numbers = @"0123456789";
-	NSMutableArray<NSString *> *numArray = [[NSMutableArray alloc] init];
+	NSMutableArray<NSString *> *numArray = [[[NSMutableArray alloc] init] autorelease];
 	for (NSUInteger x = 0; x < numbers.length; x++) {
 		unichar c = [numbers characterAtIndex:x];
 		[numArray addObject:[NSString stringWithCharacters:&c length:1]];
@@ -323,7 +323,7 @@ - (NSArray *)overloadNumbers {
 - (NSArray *)overloadFnKeys {
 #ifdef __IPHONE_13_4
 	if (@available(iOS 13.4, *)) {
-		NSArray<NSString *> *fnKeys = [[NSArray alloc] initWithObjects:UIKeyInputF1, UIKeyInputF2, UIKeyInputF3, UIKeyInputF4, UIKeyInputF5, UIKeyInputF6, UIKeyInputF7, UIKeyInputF8, UIKeyInputF9, UIKeyInputF10, UIKeyInputF11, UIKeyInputF12, nil];
+		NSArray<NSString *> *fnKeys = [[[NSArray alloc] initWithObjects:UIKeyInputF1, UIKeyInputF2, UIKeyInputF3, UIKeyInputF4, UIKeyInputF5, UIKeyInputF6, UIKeyInputF7, UIKeyInputF8, UIKeyInputF9, UIKeyInputF10, UIKeyInputF11, UIKeyInputF12, nil] autorelease];
 		return [self overloadKeys:fnKeys withSelector:@selector(handleFnKey:)];
 	}
 #endif
@@ -332,7 +332,7 @@ - (NSArray *)overloadFnKeys {
 
 - (NSArray *)overloadSpecialKeys {
 #ifdef __IPHONE_13_4
-	NSMutableArray<NSString *> *specialKeys = [[NSMutableArray alloc] initWithObjects:UIKeyInputEscape, UIKeyInputPageUp, UIKeyInputPageDown, nil];
+	NSMutableArray<NSString *> *specialKeys = [[[NSMutableArray alloc] initWithObjects:UIKeyInputEscape, UIKeyInputPageUp, UIKeyInputPageDown, nil] autorelease];
 
 	if (@available(iOS 13.4, *)) {
 		[specialKeys addObject: UIKeyInputHome];
@@ -479,7 +479,7 @@ - (void)handleSpecialKey:(UIKeyCommand *)keyCommand {
 }
 
 - (NSArray *)keyCommands {
-	NSMutableArray<UIKeyCommand *> *overloadedKeys = [[NSMutableArray alloc] init];
+	NSMutableArray<UIKeyCommand *> *overloadedKeys = [[[NSMutableArray alloc] init] autorelease];
 	// Arrows
 	[overloadedKeys addObjectsFromArray:[self overloadArrowKeys]];
 	// Roman letters