Move bsearch_arg to src/port

Tomas Vondra <tomas.vondra@postgresql.org>

Commit: bfa2cee784125047771db2768fcf7f04d8bd6bb4
Author: Tomas Vondra <tomas.vondra@postgresql.org>
Date: 2021-03-22T23:11:22Z
Releases: 14.0
Move bsearch_arg to src/port

Until now the bsearch_arg function was used only in extended statistics
code, so it was defined in that code.  But we already have qsort_arg in
src/port, so let's move it next to it.

Files