[COC] Support usage of multiple `spawn_loadout` sections in character descriptions.

Created by: Neloreck

Allows addition of sections spawn_loadout, spawn_loadout2 ... spawn_loadoutN for stalkers items randomization. Definition of rifle + pistol character description becomes simpler and more readable.

Related

https://github.com/OpenXRay/xray-16/issues/1529

Changes

• Similar to CoC support few loadouts in character description
• Reformat code with clang-format

Todo / future

• Support silencer/scope probability to spawn? (in CoC it is done with lua script)
• Add callback for script based handling of loadouts (https://github.com/revolucas/CoC-Xray/blob/master/src/xrGame/alife_object.cpp#L29)

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Regarding script callback:

• In CoC it has very specific name, CSE_ALifeObject_spawn_supplies - prettier/shorter variant could be used
• In CoC it is bound to ai_stalker file

It is just few lines of code, but I am not sure about naming of the callback.