Binary search for ProjectilePrediction()

[acidtripparty]

Two improvements:

• Use binary search for time prediction in ProjectilePrediction(). We get very tight mindelta with same time complexity. (Flag: debug.pp-bsearch)
• Account for projectile gravity drop. (Flag: debug.pp-gravity)

Both changes are gated by the flags. No-op code change -- should not affect existing configs.

[LemonatedCat]

Testing today.

[LemonatedCat]

Works just fine

[LemonatedCat]

Actually nevermind, it often just sits there and does not even try to shoot