MBF21 Codepointer updates

[XaserAcheron]

Updates the following codepointers to make good use of the extended arg range:

• A_SpawnObject(type, angle, x_ofs, y_ofs, z_ofs, x_vel, y_vel, z_vel)
  • All 8 args used :D
  • Also renamed this function from A_SpawnFacing to A_SpawnObject since the new name suits it better now.
• A_MonsterProjectile(type, angle, pitch, hoffset, voffset)
• A_MonsterBulletAttack(hspread, vspread, numbullets, damagebase, damagedice)
• A_WeaponProjectile(type, angle, pitch, hoffset, voffset)
• A_WeaponBulletAttack(hspread, vspread, numbullets, damagebase, damagedice)

Also updated mbf21.md with better descriptions of everything, including the new args; refer to it for specifics.