all games: Add sv_infinite_ammo ConVar

[copperpixel]

This PR implements the sv_infinite_ammo cheat-protected ConVar from Left 4 Dead/Alien Swarm. When enabled, it prevents the player's active weapon from depleting ammo.
Furthermore, added functionality from Counter-Strike : GO where setting the ConVar to 2 or higher will only replenish the weapon's reserve (so the player still has to reload).

In Team Fortress 2, it also refills metal and weapon/item charges.

[copperpixel]

This doesn't seem to work with energy weapons in TF2

Should be fixed now

[brokenparts]

This seems to work perfectly for guns.

If you want to refill Soldier banners and rage meters (Soda Popper, Phog, Hitman's Heatmaker, etc) the simpler way to do it would be by calling CTFPlayerShared::SetItemChargeMeter on every weapon slot. This is what impulse 101 does:

source-sdk-2013/src/game/server/tf/tf_player.cpp

Lines 14760 to 14766 in 0565403

	m_Shared.m_flRageMeter = 100.f;
	m_Shared.SetDemomanChargeMeter( 100.f );
	for( int i = FIRST_LOADOUT_SLOT_WITH_CHARGE_METER; i <= LAST_LOADOUT_SLOT_WITH_CHARGE_METER; ++i )
	{
	m_Shared.SetItemChargeMeter( (loadout_positions_t)i, 100.f );
	}

[copperpixel]

Added your suggested changes, thanks! Although the SetScoutHypeMeter call is still needed as the Soda Popper charge doesn't seem to be affected by SetRageMeter and SetItemChargeMeter (impulse 101 doesn't affect it either).

[brokenparts]

That may have just been an issue with my testing setup, then.