pgsql: Add test_pg_dump to @contrib_excludes

Add test_pg_dump to @contrib_excludes

The test_pg_dump extension doesn't have a C component, so we need
to exclude it from the MSVC build system trying to figure out how
to build it.

Also add a "MODULES" line to the Makefile, as test_extensions has.
Might not be necessary, but seems good to keep things consistent.

Lastly, remove the 'installcheck' line from test_pg_dump, as that
was causing redefinition errors, at least on my box. This also
makes test_pg_dump consistent with how commit_ts is set up.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/6e243c43c9b2d35f91a73d3982db6a0cad0eb64b

Modified Files
--------------
src/test/modules/test_pg_dump/Makefile | 4 +---
src/tools/msvc/Mkvcbuild.pm | 2 +-
2 files changed, 2 insertions(+), 4 deletions(-)