Correct the definition of ObjC's BOOL in our pre-canned set of defines.  It's supposed to
be "signed char" not "int".

<rdar://problem/13131126>


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@174209 91177308-0d34-0410-b5e6-96231b3b80d8