adding extra error check in LEInteractor for spreading near physical boundaries
updating ghost cell width for some variables
fixing abs() for gcc
Merge branch 'master' of https://github.com/IBAMR/IBAMR

Merging latest ibamr
Interpolation check added for example
Merge branch 'master' into amneetb/RigidIBFE

Merging latest changes from master.
force normalization added for KrylovMobilityInverse