Plant damage, Land Mine, minor fixes and improvements
- Fixed up the damage code in regards of damage against plants (bugreport:9380)
  * Rewrote DAMAGE_DIV_FIX so that it rounds damage down when number of hits is negative (damage split on hits)
  * Created a function battle_apply_div_fix that does not only call DAMAGE_DIV_FIX but also makes sure that damage can only become 0 when the custom config setting skill_min_damage is not set for the current skill type
  * skill_min_damage is now 0 by default (official: all types can fail against plants as long as skills have negative number of hits), if set, all skills will deal as much damage as hits
  * Restructured and renamed function now known as "is_infinite_defense" that will work for all 3 damage types and returns if damage is infinite for the current situation, it will now also properly consider all "MD_IGNORE" modes
  * Fixed the order of processing of all 3 skill types in regards of plant damage: first all calculations are done, then plant damage is applied and then DAMAGE_DIV_FIX is applied
  * Sonic Blow and Rapid Shower are now skills with negative number of hits (i.e. they can't hit plants officially)
  * Traps can no longer ignore plant mode (only way to damage plant more is via status changes)
  * Final Strike is now able to hit plants (deals 1 HP damage)
  * When left-hand-wielding, you will now always deal 2 damage to plants per attack, regardless of whether double attack triggers or you don't even have a weapon in the right hand
  * There will no longer be backhand damage to plants (Katar)
- Land Mine is now a single target skill, the trap still triggers in a 3x3 area, but will only hit the first target that touches it (issue:99)
- Changed the "Don't return reflect damage" flag from 0x1000 to 0x1000000 as apparently the other flag was already used; updated function description so it's easier to see
- Improved SC_SIGHTBLASTER structure slightly
- Typo fixes and description improvements