Refactor \x processing to single function

Refactor \x processing to single function

There are three places that process \x.  These can and did get out of
sync.  This moves all three to use a common static inline function so
that they all do the same thing on the same inputs, and their behaviors
will not drift apart again.

This commit should not change current behavior.  A previous commit
was designed to bring all three to identical behavior.