err_attribute_not_string has been subsumed by err_attribute_argument_type.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@187400 91177308-0d34-0410-b5e6-96231b3b80d8
Added the notion of Type and TargetSpecific attributes to the clang tablegen.  In turn, this fixes a mistake with Ptr32, Ptr64, UPtr and SPtr attribtues generating AST nodes that are never actually used.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@187401 91177308-0d34-0410-b5e6-96231b3b80d8