Allow building compilerplugins/clang on Mac OS X

(at least against a self-built Clang configured --enable-keep-symbols)

Change-Id: I6e38688c78f78aca1864530042159cdcef7a0694
ParentBuilder needs support for ObjCMethodDecl

Change-Id: I8883649da31eabbc5a0f9780fb953ad58f154e1e
Handle ImplicitCastExpr w/ invalid loc from Objective C code

Change-Id: I82cb8aa53ea5fd86d6ff46af876dd3f55e1123d1
implicitboolconversion: support for Objective C BOOL

Change-Id: Id63f42fa8875211af9f41c21f3fa128403f8a880
Special handling of __builtin_expect in boolean expressions

...as found in Mac OS X' assert macro definition,

  __builtin_expect(!(e), 0) ? ... : ...

with type

  long __builtin_expect(long, long)

The code in literaltoboolconversion.cxx is needed for

  assert(false);

Change-Id: I42f87482c56986af74b2ec849db9852f74c7c938
Adapt vcl to various loplugin warnings on Mac OS X

Change-Id: I4553ce218fbcf2ac681b284c71e7d558a451511c
-Werror,-Wunused-function

Change-Id: Ic792930c291bae1cf18ffd65548908e910c69c45