check_libs: ignore /var/lib/postgresql/

it contains only data and produces false-positives like this:
adding postgres(5733) because of [/var/lib/postgresql/9.2/main/pg_xlog/000000010000002D000000F9 (deleted)]:
check_libs: ignore /var/log/
Merge pull request #16 from evgeni/master

check_libs: ignore /var/lib/postgresql/ and /var/log/