Revert "Rename F_{None,Text,Append} to OF_{None,Text,Append}. NFC"

This reverts commit 58c814614d2ac69bcf79b09543505fac80ada4e6.
Fixes build breakage using LLVM<7.

git-svn-id: https://llvm.org/svn/llvm-project/libclc/trunk@367893 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed