package/proftpd: add mod_{sql, quotatab} support

package/proftpd: add mod_{sql, quotatab} support

- Enables mod_sql which is required for quotatab_sql
- Adds options for enabling mod_quotatab and the sub-component
  file/LDAP/RADIUS/SQL modules
- Copies over ftpquota script if perl and mod_quotatab are
  enabled (This script isn't required but is an additional tool
  for mod_quotatab)

Signed-off-by: Paresh Chaudhary <paresh.chaudhary@rockwellcollins.com>
Signed-off-by: Matt Weber <matthew.weber@rockwellcollins.com>
Signed-off-by: Jared Bents <jared.bents@rockwellcollins.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>