Warning for framework headers using double quote includes

Introduce -Wquoted-include-in-framework-header, which should fire a warning
whenever a quote include appears in a framework header and suggest a fix-it.
For instance, for header A.h added in the tests, this is how the warning looks
like:

./A.framework/Headers/A.h:2:10: warning: double-quoted include "A0.h" in framework header, expected angle-bracketed instead [-Wquoted-include-in-framework-header]
#include "A0.h"
         ^~~~~~
         <A/A0.h>
./A.framework/Headers/A.h:3:10: warning: double-quoted include "B.h" in framework header, expected angle-bracketed instead [-Wquoted-include-in-framework-header]
#include "B.h"
         ^~~~~
         <B.h>

This helps users to prevent frameworks from using local headers when in fact
they should be targetting system level ones.

The warning is off by default.

Differential Revision: https://reviews.llvm.org/D47157

rdar://problem/37077034

llvm-svn: 335184