[objcmt] Rewrite a NSDictionary dictionaryWithObjects:forKeys: to a dictionary literal

if we can see the elements of the arrays.

for example:

 NSDictionary *dict = [NSDictionary dictionaryWithObjects:[NSArray arrayWithObjects:@"1", @"2", nil] forKeys:[NSArray arrayWithObjects:@"A", @"B", nil]];

-->

 NSDictionary *dict = @{ @"A" : @"1", @"B" : @"2" };

rdar://12428166

llvm-svn: 172679