Expands gunmod compatability a bit in order to better take advantage of the new gunmod slot system.
Merge pull request #6576 from Rivet-the-Zombie/mod-tweaks

Expands gunmod compatability a bit in order to better take advantage of the new gunmod slot system.
Gives hairpins improvised picklock functionality.
DURABLE_MELEE is a flag, not a technique
Merge pull request #6594 from Izicata/patch-12

DURABLE_MELEE is a flag, not a technique
Merge branch 'hairpin-lockpick' of https://github.com/Rivet-the-Zombie/Cataclysm-DDA into Rivet-the-Zombie-hairpin-lockpick