Fix mistakes in pg_ctl's code for "start -w" that tries to cope with

Fix mistakes in pg_ctl's code for "start -w" that tries to cope with
non-default settings for the postmaster's port number.  The code to parse
command line options and postgresql.conf entries wasn't quite right about
whitespace or quotes, and it was coded in a not-very-readable way too.
Per bug #3969 from Itagaki Takahiro, though this is more extensive than his
proposed patch (which fixed only the whitespace problem).
This code has been broken since it was put in in 8.0, so patch all the way
back.