pgsql-server: Add mention of environment variable conflict with

Log Message:
-----------
Add mention of environment variable conflict with uncommenting config
file variables:

< Another option is to allow commented values to return to their
< default values.

This has to address environment variables that are then overridden
by config file values. Another option is to allow commented values
to return to their default values.

Modified Files:
--------------
pgsql-server/doc:
TODO (r1.1338 -> r1.1339)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/doc/TODO.diff?r1=1.1338&amp;r2=1.1339)