Reorder the DIFile parameter in DINameSpace

Moving the DIFile parameter to immediately proceed the tag so that it will be a
common prefix with other DIScopes (once the DIFile is replaced with the raw
file/directory pair).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177492 91177308-0d34-0410-b5e6-96231b3b80d8