PL/Ruby 0.6.0

tests: fix conv_geometry test-case

Seems like ruby's yield keyword changed so it doesn't return array
nowadays -- ensure we yield an _array_ (of the same size as the
SETOF type).

Fixes: #13

0.5.7

Revert "more fixes for 0.5.6"

This reverts commit 724ab4fea0a5e6949e3d122400de39a610cb2a7a.

0.5.6

Release 0.5.6 with some more patches applied from Fedora.

plruby-0.5.5

Apply several patches from Fedora, that fixes build issues with PostgreSQL 9.1+ and Ruby 2.2 and newer GCCs.