a new NamedDecl::getAsString() method.

Change uses of Selector::getName() to just pass in a Selector 
where possible (e.g. to diagnostics) instead of going through
an std::string.

This also adds new formatters for objcinstance and objcclass
as described in the dox.

llvm-svn: 59933

Refactored error reporting in CheckObjCDealloc and CheckObjCInstMethSignature to use this new bug reporting interface (major code simplification).

llvm-svn: 53560

llvm-svn: 53493

ObjCImplementationDecls and sees if a ancestor class defines a method with the
same selector but with a different type signature. Right now it just compares
return types, and mainly looks at differences in primitive values. The checking
will be expanded in the future.

llvm-svn: 53482