Add CS_DMG_THROW to cstrike.inc

[Bara]

I added this in cstrike.inc, because I don't know which other games has throwable weapons/items which make damage.

I already use this in one of my plugins and it works pretty good.

[asherkin]

This already exists in the sdkhooks include as DMG_CLUB (and the name makes sense, so I don't think we need an extra definition).

[Bara]

Oh, I didn't saw that. If it works, then we can close this PR.