Name       : F_BACKSTAB_HIT(bs, dex, aware, def)

Defined in : <formulas.h>

Description: Calculate the to-hit value of the backstab attempt.

Arguments  : (int)bs    - the backstab skill of the attacker.
             (int)dex   - the dexterity of the attacker.
             (int)aware - the awareness skill of the victim.
             (int)def   - the defence skill of the victim.

Returns    : (int) the to-hit value.