Remove old backwards compatibility support from the parser for autoupgrading

Remove old backwards compatibility support from the parser for autoupgrading
the old malloc/free instructions, and for 'sext' and 'zext' as function
attributes (they are spelled signext/zeroext now), and support for result
value attributes being specified after a function.

Additionally, diagnose invalid attributes on functions with an error message
instead of an abort in the verifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@133229 91177308-0d34-0410-b5e6-96231b3b80d8