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

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

llvm-svn: 367893
GitOrigin-RevId: 2b30f0ee7314e704a2500effb4974e4adb7c01d5
1 file changed