V55 COMPILE FIX

Fixes
- Adds local integer helper functions stamp_min_int() and stamp_max_int().
- This fixes the MinGW build error from V54: implicit declaration of max_int/min_int.

Includes previous V54 behaviour
- Point-click finite-fault patches are reconstructed into a continuous brush-like mask first.
- Secondary deformation is generated as a soft halo around that mask boundary.
