LoW: added local ELVISH_MOUNTED_UNITS macro in Saurian Treasury.

This macro, unlike the unit types lists that will replace, includes also Elvish Horse Archers.
LoW: replaced three unit types lists with ELVISH_MOUNTED_UNITS macro
LoW: avoid firing the reached treasury event in Saurian Treasury if the Elvish unit isn't a mounted one
LoW: used SUF in [remove_unit_overlay]; also deleted no longer useful [store_unit] and CLEAR_VARIABLE
LoW: corrected filter in Bounty Hunters, so the player's loyal unit stay in the recall list, even if they reached level 3
LoW: removed a stray [part] title= in The Chief Must Die
Changelog entries for my previous commits