When declaring an Objective-C implementation without a corresponding

interface, suggest correction of typos. For example, given:

  @interface NSString
  @end

  @implementation NSstring
  @end

we'll warn with:

t.m:4:19: warning: cannot find interface declaration for 'NSstring';
    did you mean 'NSString'?
  @implementation NSstring
                  ^

However, since this is just a warning, we don't provide a fix-it
hint. Good idea, Ted!

llvm-svn: 92488