change getCurFunctionDecl to skip through Block contexts to find

change getCurFunctionDecl to skip through Block contexts to find
the containing block.  Introduce a new getCurFunctionOrMethodDecl
method to check to see if we're in a function or objc method.
Minor cleanups to other related places.  This fixes rdar://6405429.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@60564 91177308-0d34-0410-b5e6-96231b3b80d8