pgsql: When system() fails in Win32, report it as an exception, print

Log Message:
-----------
When system() fails in Win32, report it as an exception, print the
exception value in hex, and give a URL where the value can be looked-up.

Modified Files:
--------------
    pgsql/src/backend/postmaster:
        postmaster.c (r1.508 -> r1.509)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/postmaster.c.diff?r1=1.508&r2=1.509)
    pgsql/src/include/port:
        win32.h (r1.65 -> r1.66)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/port/win32.h.diff?r1=1.65&r2=1.66)
    pgsql/src/port:
        exec.c (r1.44 -> r1.45)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/port/exec.c.diff?r1=1.44&r2=1.45)