pgsql: Add more detail to error message for invalid arguments for serve

Add more detail to error message for invalid arguments for server process

It now prints the argument that was at fault.

Also fix a small misbehavior where the error message issued by
getopt() would complain about a program named "--single", because
that's what argv[0] is in the server process.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/86947e666d39229558311d7b0be45608fd071ed8

Modified Files
--------------
src/backend/tcop/postgres.c | 31 ++++++++++++++++++++++---------
1 files changed, 22 insertions(+), 9 deletions(-)