pgsql: Install TAP test infrastructure so it's available for extension

Install TAP test infrastructure so it's available for extension testing.

When configured with --enable-tap-tests, "make install" will now install
the Perl support files for TAP testing where PGXS will find them.
This allows extensions to rely on $(prove_check) even when being built
out-of-tree.  Back-patch to 9.4 where we first started to support TAP
testing, to reduce the number of cases extension makefiles need to
consider.

Craig Ringer

Discussion: 

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/c3a0818460a8f4a5e1a9109b035ac30e84b7e06f

Modified Files
--------------
src/Makefile           |  3 ++-
src/test/Makefile      |  2 +-
src/test/perl/Makefile | 33 +++++++++++++++++++++++++++++++++
3 files changed, 36 insertions(+), 2 deletions(-)