Moving other hex functions to /common

I now understand the wisdom of moving the remaining hex functions to
/common.  I know someone already suggested that, and the attached patch
does this.

I will add the attached patch to the commitfest so I can get cfbot
testing.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EnterpriseDB                             https://enterprisedb.com

  The usefulness of a cup is in its emptiness, Bruce Lee