Implement scrollhop-like submode for bhop

[Panzerhandschuh]

The purpose of this mode is to restore the original challenge and gameplay on maps like bhop_exodus, kz_bhop_benchmark, bhop_depot, and bhop_arcane while fixing the inherent randomness with CS:S scroll hop. A small input buffer (50ms?) will be added that allows the player to queue their next jump. Early jump inputs will be penalized with an increasing ground friction penalty (up to 5 frames of ground friction at 50ms?).

"Stamina Hop", "Tech Hop", or "KZ Hop" might be more appropriate names since this mode doesn't require using scroll to time your jumps.

This mode will be enabled by a cvar: mom_bhop_mode

• mom_bhop_mode 0 - Standard autohop mode
• mom_bhop_mode 1 - Buffered autohop with stamina and ground friction penalty, 100 aa/ticks

This mode will be implemented in 3 phases:

1. Re-add CS:S stamina code
2. Apply ground friction every time the player autohops
3. Replace autohop with buffered jumps, scale the ground friction based on how early the player times their jump

Phase 3 is highly subjective and will require some time balancing to make the difficulty as close to CS:S scrollhop as possible. Some potential alternative mechanics to try out:

• Replace the 50ms autohop input buffer with Quake-style buffered jumping where you have to be holding jump while landing to autohop. This change would force the player to jump with spacebar/mouse click instead of scroll wheel.
• Replace the ground friction penalty with a speed penalty that applies while the player is holding jump in the air (similar to how acceleration is reduced while holding jump in Defrag). This change would make it so you have to time your +jump input right before landing and -jump right after landing for optimal speed.
• Use fixed ground friction instead of scaling it based on timing error. I've heard this get suggested, but I think it would only work well with Quake-style buffered jumps or autohop. The 50ms input buffer can easily be exploited with hyperscroll or jump spam macros.

[Panzerhandschuh]

Phase 1 is complete. The new cvar for enabling stamina is mom_mv_stamina_enabled