bug report: 7.4beta3 pg_ctl log handling

Simplest case to test is:

pg_ctl start -D /valid/db/dir -l /invalid/dir
pg_ctl: /invalid/dir: No such file or directory
postmaster successfully started

Postmaster hasn't started and the error could probably use some work.

Perhaps some more tests after line 340 of pg_ctl would be appropriate.
Something along the lines of (perlish pseudocode):

if ( -w $logfile || ( -w `dirname $logfile` )

Should it also test -O to ensure ownership if the file does exist? I'll
brush up on my sh and submit a patch if requested.