Correct HHVM version to 3.15.2+

php 7.1 with MARIADB_VERSION=10.1 seems to no longer be erroring randomly on tests

to correctly install and test the pgsql versions it looks like we are gong to have to long form the matrix with each of the pgsql versions

try to only add when pgsql

POSTGRESQL_VERSION=9.6 was released September 2016 See if we can run it on travis

Additionally allowing failures on PHP 7.1 with mariadb MARIADB_VERSION=10.1 since it is intermittently erroring

- fixes version of HHVM being tested
- drops mariadb 5.5
- adds POSTGRESQL_VERSION=9.5 (only available with sudo enabled trusty)

Handle arbitrary whitespaces when parsing SQL in order to apply LIMIT for MS SQL Server

Merge branch 'fix/#2318-fix-listing-table-columns-when-using-external-or-os-authentication-on-oracledb'

Close #2318
Close DBAL-831

Close #2302
Close #2303

fixes #2302

Close #2287
Close #1183

- includes extended default driver connection parameter handling
- minor refactoring

fixes #1183

Close #2182
Close #2277
Close DBAL-939

- fixes platform's COMMENT ON statement support
- implements reverse engineering for column comments
- marks boolean column type commented for distinction

fixes #2182

Close #2500
Close #2497

Close #2494