[clang] Enable printf check for CFIndex

According to 
https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/Strings/Articles/formatSpecifiers.html
CFIndex and NSInteger should be treated the same way (see the section Platform Dependencies).
This diff changes the function shouldNotPrintDirectly in SemaChecking.cpp accordingly 
and adds tests for the "fixit" and the warning.

Differential revision: https://reviews.llvm.org/D34496

Test plan: make check-all

llvm-svn: 306343