MTRS.2DA minor update

[devSin]

Small trolls don't have sounds (like most everything in BG2, this was copied from IWD, but the sounds don't actually exist). Luckily, Black Isle had fairly strict naming conventions, so we can just swap the base to use the normal troll sounds (also copied from IWD).

COPY_EXISTING ~Mtrs.2da~ ~override~
 REPLACE_TEXTUALLY ~ICETR~ ~TROLL~
BUT_ONLY_IF_IT_CHANGES

[CamDawg]

Included in alpha 4.