Remove Multidefs

Remove Multidefs

Multidefs are a bit unwieldy and incomplete.  Remove them in favor of
another mechanism, probably for loops.

Revert "Make Test More Thorough"
Revert "Fix a typo."
Revert "Vim Support for Multidefs"
Revert "Emacs Support for Multidefs"
Revert "Document Multidefs"
Revert "Add a Multidef Test"
Revert "Update Test for Multidefs"
Revert "Process Multidefs"
Revert "Parser Multidef Support"
Revert "Lexer Support for Multidefs"
Revert "Add Multidef Data Structures"

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@141378 91177308-0d34-0410-b5e6-96231b3b80d8