For consistency with normal instructions and clarity when reading IR,
it's best to print the %0, %1, ... names of function arguments in
definitions.
Also modifies the parser to accept IR in that form for obvious reasons.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@367755 91177308-0d34-0410-b5e6-96231b3b80d8
7ff3d073b5