pgsql: Regression makefile now needs to make separate lists of what to

Log Message:
-----------
Regression makefile now needs to make separate lists of what to clean
for input/ and output/ directories, because with the addition of
largeobject_1.source, they're not the same list.  Apparently the current
buildfarm process does not exercise whether 'make distclean' leaves a
clean tree behind, else the farm would have been failing for awhile.

Modified Files:
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    pgsql/src/test/regress:
        GNUmakefile (r1.66 -> r1.67)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/GNUmakefile.diff?r1=1.66&r2=1.67)