allow snapping to vertex and segment to remove part/ring
Fix 'geos_c.h not found' build error on Mac
update lib paths for phonon_backends
Added connection pool for SpatiaLite, improving rendering speed within one DB

- refactored PostgreSQL connection pool into generic template classes
- used the template classes for SpatiaLite connection pool
- pooled SpatiaLite connections are opened with SQLITE3_OPEN_NOMUTEX flag to allow parallel access
Merge pull request #1128 from 3nids/removesnapsegment

allow snapping to vertex and segment to remove part/ring