objective-C: clang must implicitly convert

__objc_yes/__objc_no to (BOOL)1/(BOOL)0 when
BOOL is declared; otherwise it resorts to
default of 'signed char'. This is important to
selecting the correct Numeric API numberWithBool:
Can't have a clang test for this. Will checkin and
executable llvm test. // rdar://12156616

llvm-svn: 162922