Lookup methods in the global pool even when a statically typed object's class interface isn't in scope!

As the comment in the code indicates, I'm not fond of this. Nevertheless, gcc compat is a goal.

Here is the case I'm talking about...

#import <Foundation/Foundation.h>

@interface AnyClass : NSObject
- (NSRect)rect;
@end

@class Helicopter;

static void func(Helicopter *obj) {
  NSRect r = [obj rect];
}

...before this patch, we would warn/error. With this patch, everything "just works".

llvm-svn: 44682