pgsql: Allow pg_regress to be run outside the build tree.

Log Message:
-----------
Allow pg_regress to be run outside the build tree. Look for input files
in both input and output dir, to handle vpath builds more simply.

Modified Files:
--------------
pgsql/src/makefiles:
pgxs.mk (r1.12 -> r1.13)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/makefiles/pgxs.mk?r1=1.12&r2=1.13)
pgsql/src/pl/plperl:
GNUmakefile (r1.34 -> r1.35)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/pl/plperl/GNUmakefile?r1=1.34&r2=1.35)
pgsql/src/pl/plpython:
Makefile (r1.29 -> r1.30)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpython/Makefile?r1=1.29&r2=1.30)
pgsql/src/pl/tcl:
Makefile (r1.51 -> r1.52)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/pl/tcl/Makefile?r1=1.51&r2=1.52)
pgsql/src/test/regress:
GNUmakefile (r1.74 -> r1.75)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/GNUmakefile?r1=1.74&r2=1.75)
pg_regress.c (r1.47 -> r1.48)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/pg_regress.c?r1=1.47&r2=1.48)
pg_regress.h (r1.3 -> r1.4)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/pg_regress.h?r1=1.3&r2=1.4)
pg_regress_main.c (r1.3 -> r1.4)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/pg_regress_main.c?r1=1.3&r2=1.4)
pgsql/src/test/regress/input:
create_function_1.source (r1.18 -> r1.19)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/input/create_function_1.source?r1=1.18&r2=1.19)
create_function_2.source (r1.15 -> r1.16)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/input/create_function_2.source?r1=1.15&r2=1.16)
pgsql/src/test/regress/output:
create_function_1.source (r1.32 -> r1.33)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/output/create_function_1.source?r1=1.32&r2=1.33)
create_function_2.source (r1.21 -> r1.22)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/output/create_function_2.source?r1=1.21&r2=1.22)