Mantis 2.0 - Database Layer Patch

This patch replaces the ADODB database layer which is known-broken for
non-mysql database e.g. postgres, mssql, oracle in Mantis with a new layer
that:

a) provides supported postgres, mssql and oracle support within Mantis

b) Provides a php memory/performance increase over the existing database
layer for mysql users

Resolves Mantis Issues:

#0017189: mc_projects_get_user_accessible() produces a mysql error