Fix constraints checks in grompp

This adds F_CONSTRNC to the set of interactions that should trigger
checks on SHAKE and LINCS parameters, and permits the MTTK check to
test also for SETTLE for its warning. The latter will also be used to
prevent MTTK + any constraints in a subsequent patch.

Change-Id: I175a2f050623192ff35a4cf93605fcfdd909f41a