update RELEASE_NOTES, abt compat. breaking / nonbreaking changes

RELEASE_NOTES

@@ -43,11 +43,12 @@ The [filter_vision] tag introduced in 1.11 series was discovered to have some bu
 [list][*]When used in a unit filter, a [filter_vision] check succeeds if there is [b]any[/b] side with vision of the unit (no fog there and unit is not hiding from that side) which passes the side filter in [filter_vision], and fails otherwise.
 [*] When used in a terrain_filter, a [filter_vision] check succeeds if there is [b]any[/b] side with vision of the location (no fog there, or if respect_fog=false, then no shroud there) which passes the side filter in [filter_vision], and fails otherwise.
 [/list]
+Note that the above is a compatibility breaking change! Please double-check the behavior of any scenario which is using this tag.
 
 The [allied_with] / [enemy_of] tags in side filter had some related issues -- they were originally intended to match if *any* side matches the filter, but they
 ended up being implemented in a needlessly confusing manner, where they in most cases match if *all* sides matching the filter are allies / enemies, but if 
 there are none then they report false anyways. To work around this [has_ally] and [has_enemy] have been added, which correctly match when *any* side matching 
-the filter is an ally or enemy.
+the filter is an ally or enemy. ([allied_with] and [enemy_of] have not been changed.)
 
 Thus excepting for [allied_with] / [enemy_of], all filters in 1.11.16+ are simply a check for *any* object matching the filter data.
 [/section]