pgsql: Avoid version-control system directories when creating TAGS.

Log Message:
-----------
Avoid version-control system directories when creating TAGS. Besides
being wasteful, this can collide with repostory metadata on case-insensitive
file sytems.

Modified Files:
--------------
pgsql/src/tools:
make_etags (r1.4 -> r1.5)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/tools/make_etags?r1=1.4&r2=1.5)