Adding mouse support for SDL builds. Currently used for:
Look around:
* Left click to move cursor

Targeting:
* Left click to move cursor
* Scrollwheel to cycle targets
* Right click to fire
Use input_event struct to encapsulate mouse events
Fix 'if' block missing braces and const correctness
With circular distances on, make circular craters
Add a return statement to dummy getch_kyb_mouse definition in wincurses, in case that's causing some compilers to complain.
Fix food [a]ctivate
prevent inventory duplication on [a]ctivate, fixes clothing activation.
[a]ctivate lists all activatables.
Added more pack monster spawns.
Removed effect of sound on dynamic spawning.
Added Shia back to the game, gave him similar spawning to jabberwocky but rarer
Accidently spawned more jabberwocks instead of shias. Fixed.
Merge pull request #3726 from ianestrachan/circular-craters

Craters circles instead of squares
Renames retool kits.
Fix unnecessary debug spam about CARGO parts.
Move input_event into a common input definitions header that can be shared with Cygwin and Linux build configurations.
Merge pull request #3745 from ianestrachan/fix-cargo-debug-msg

Fix unnecessary debug spam about CARGO parts.
Merge basic mouse support.
Final build fix for mouse support.
Merge fix returning activate to universiality.
Merge pull request #3743 from Rivet-the-Zombie/Recaliber-rename!

Renames retool kits.