Update base_npcs.lua

[Blixibon]

• Medics can now heal allies, including Alyx, Barney, and even Vortigaunts. (caused by being in same squad)
• Medics will drop a health vial when they die.
• Zombies/Headcrabs and Antlions have their own squads.
  • Poison Zombies and Poison Headcrabs are in a different squad.
• Vortigaunt Slaves are not in a squad. (unless they smuggle things, another reason not to trust these vorts)

Basically, everyone is in a squad now except for actor-derived NPCs like Kleiner or Breen who lack the AI required to make squads plausible.

[Bo98]

Why use raw values here and not bit.bor( SF_NPC_DROP_HEALTHKIT, SF_CITIZEN_MEDIC )?

[Blixibon]

I wrote that code about 5 months ago for a NPC enhancement mod, and I've always thought bit.bor only accepted integers. This is before I understood exactly what SF_FLAG_HERE definitions were, thinking they were only lua hooks at the time. I didn't think about it very much while making this pull request, except for wondering if there's another way to include multiple spawnflags.

I'll fix it as soon as possible.

[robotboy655]

I guess I should've seen this one coming...

[Kefta]

Guess he pulled a code_gs

[Blixibon]

I'm assuming I made this mistake when I updated the code to fit the recent base_npcs.lua revamp. Thank you for fixing it.