This commit adds a new predefined macro named __OBJC_BOOL_IS_BOOL that describes
the Objective-C boolean type: its value is zero if the Objective-C boolean uses
the signed character type, otherwise its value is one as the Objective-C boolean
uses the builtin boolean type.
rdar://21170440
Differential Revision: https://reviews.llvm.org/D26234
llvm-svn: 287529