Add new weapons to CSWeaponID enum. (#869)

plugins/include/cstrike.inc

@@ -152,6 +152,10 @@ enum CSWeaponID
 	CSWeapon_KNIFE_SURVIVAL_BOWIE = 514,
 	CSWeapon_KNIFE_BUTTERFLY = 515,
 	CSWeapon_KNIFE_PUSH = 516,
+	CSWeapon_KNIFE_URSUS = 519,
+	CSWeapon_KNIFE_GYPSY_JACKKNIFE = 520,
+	CSWeapon_KNIFE_STILETTO = 522,
+	CSWeapon_KNIFE_WIDOWMAKER = 523,
 	CSWeapon_MAX_WEAPONS //THIS MUST BE LAST, EASY WAY TO CREATE LOOPS. When looping, do CS_IsValidWeaponID(i), to check.
 };