Fix minor issues with new unicode {de,re}composition code

Fix minor issues with new unicode {de,re}composition code

The table generation script would incorrectly complain in the
recomposition sorting when matching code points.  This would not have
caused the generation of an incorrect table.  Note that this condition
is not reachable yet, but could have been reached with future updates.

pg_bswap.h does not need to be included in the frontend.x

Author: John Naylor
Discussion: https://postgr.es/m/CAFBsxsGWmExpvv=61vtDKCs7+kBbhkwBDL2Ph9CacziFKnV_yw@mail.gmail.com