pgsql: Make TAP test suites to work, when @INC does not contain current

Make TAP test suites to work, when @INC does not contain current dir.

Recent Perl and/or new Linux distributions are starting to remove "." from
the @INC list by default. That breaks pg_rewind and ssl test suites, which
use helper perl modules that reside in the same directory. To fix, add the
current source directory explicitly to prove's include dir.

The vcregress.pl script probably also needs something like this, but I
wasn't able to remove '.' from @INC on Windows to test this, and don't want
to try doing that blindly.

Discussion: <20160908204529(dot)flg6nivjuwp5vaoy(at)alap3(dot)anarazel(dot)de>

Branch
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REL9_4_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/b803b8823517c277bbe4bf0d1b7ea4a39b446a8b

Modified Files
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src/Makefile.global.in | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)