Called on weapon fire to decide if the current shot should be critical. Return Plugin_Continue to let the original calculation or return a higher action to override the decision with the value of 'result'
Since critical shots are also calculated client side any changes made with this will not show for the shooter. Projectile weapons such as the rocketlauncher and demoman weapons will show a critical bullet but no critical sound effect. Bullet hits should appear as expected.
forward Action TF2_CalcIsAttackCritical(int client, int weapon, char[] weaponname, bool& result)