Move two functions out of the public interface that shouldn't have ever

Move two functions out of the public interface that shouldn't have ever
been there. Also delete their redundant doxyments in favor of those in
the source file. I'm putting the doxyments for private and static
helpers into the implementation file, and only the public interface
doxyments into the header. If folks have strong opinions about this type
of split, feel free to chime in, I'm happy to re-organize.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@142087 91177308-0d34-0410-b5e6-96231b3b80d8