1) implement parser and sema support for reading and verifying attribute(warnunusedresult).
2) rename hasLocalSideEffect to isUnusedResultAWarning, inverting the sense
of its result.
3) extend isUnusedResultAWarning to directly return the loc and range
info that should be reported to the user. Make it substantially more
precise in some cases than what was previously reported.
4) teach isUnusedResultAWarning about CallExpr to decls that are
pure/const/warnunusedresult, fixing a fixme.
5) change warn_attribute_wrong_decl_type to not pass in english strings, instead,
pass in integers and use %select.
llvm-svn: 64543
Chris Lattner