Don't put generic_category in the llvm namespace.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210737 91177308-0d34-0410-b5e6-96231b3b80d8
Prefix generic_category with std::.

Sorry I missed these before.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210740 91177308-0d34-0410-b5e6-96231b3b80d8