pgsql: Avoid terminating the postmaster on a number of "can't happen"

Log Message:
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Avoid terminating the postmaster on a number of "can't happen" cases during
backend startup on Win32. Instead, log the error and just forget about
the potentially dangling process, since we can't do anything about it anyway.

Modified Files:
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    pgsql/src/backend/postmaster:
        postmaster.c (r1.585 -> r1.586)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/postmaster.c?r1=1.585&r2=1.586)