docs: harmonise use of enum sentinel description in eo files

src/lib/ecore_audio/ecore_audio.eo

@@ -8,7 +8,7 @@ enum Ecore.Audio.Format {
     ogg, [[OGG]]
     flac, [[FLAC, the Free Lossless Audio Codec]]
     mp3,  [[MP3 (not supported)]]
-    last [[Sentinel value, do not use]]
+    last [[Sentinel value to indicate last enum field during iteration]]
 }
 
 class Ecore.Audio (Efl.Object)

src/lib/ector/ector_renderer.eo

@@ -6,7 +6,7 @@ enum Ector.Quality
    best, [[Best quality]]
    good, [[Good quality]]
    fast, [[Lower quality]]
-   last, [[Sentinel]]
+   last, [[Sentinel value to indicate last enum field during iteration]]
 }
 
 abstract Ector.Renderer (Efl.Object)

src/lib/edje/edje_types.eot

@@ -134,7 +134,7 @@ enum Edje.External.Param_Type {
    bool, [[Parameter value is boolean.]]
    choice, [[Parameter value is one of a set of
              predefined string choices.]]
-   max [[Sentinel. Don't use.]]
+   max [[Sentinel value to indicate last enum field during iteration]]
 }
 
 struct Edje.External.Param {

src/lib/elementary/elm_bg.eo

@@ -10,7 +10,7 @@ enum Elm.Bg.Option
   scale, [[Scale the background image, retaining aspect ratio (default).]]
   stretch, [[Stretch the background image to fill the widget's area.]]
   tile, [[Tile background image at its original size.]]
-  last [[Sentinel value, also used to indicate errors.]]
+  last  [[Sentinel value to indicate last enum field during iteration. Also used to indicate errors]]
 }
 
 class Elm.Bg (Elm.Layout, Efl.File)

src/lib/elementary/elm_calendar.eo

@@ -37,7 +37,7 @@ enum Elm.Calendar.Weekday
    thursday, [[Thursday weekday]]
    friday, [[Friday weekday]]
    saturday, [[Saturday weekday]]
-   last [[Sentinel value to mark last entry]]
+   last  [[Sentinel value to indicate last enum field during iteration]]
 }
 
 enum Elm.Calendar.Select.Mode

src/lib/elementary/elm_dayselector.eo

@@ -14,7 +14,7 @@ enum Elm.Dayselector.Day
    thu,    [[Indicates Thursday.]]
    fri,    [[Indicates Friday.]]
    sat,    [[Indicates Saturday.]]
-   max     [[Sentinel value, don't use.]]
+   max     [[Sentinel value to indicate last enum field during iteration]]
 }
 
 class Elm.Dayselector (Elm.Layout)

src/lib/elementary/elm_general.eot

@@ -92,7 +92,7 @@ enum Elm.Policy
 
                @since 1.8
              ]]
-   last
+   last [[Sentinel value to indicate last enum field during iteration]]
 }
 
 enum Elm.Policy.Quit
@@ -177,7 +177,7 @@ enum Elm.Wrap.Type
    char,     [[Char wrap - wrap between characters.]]
    word,     [[Word wrap - wrap in allowed wrapping points (as defined in the unicode standard).]]
    mixed,    [[Mixed wrap - Word wrap, and if that fails, char wrap.]]
-   last
+   last      [[Sentinel value to indicate last enum field during iteration]]
 }
 
 enum Elm.Focus_Direction

src/lib/elementary/elm_interface_fileselector.eo

@@ -10,7 +10,7 @@ enum Elm.Fileselector.Mode
    legacy: elm_fileselector;
    list = 0, [[Layout as a list.]]
    grid, [[Layout as a grid.]]
-   last [[Sentinel (helper) value, not used.]]
+   last [[Sentinel value to indicate last enum field during iteration]]
 }
 
 enum Elm.Fileselector.Sort
@@ -24,7 +24,7 @@ enum Elm.Fileselector.Sort
    by_size_desc, [[Sort by descending file size]]
    by_modified_asc, [[Sort by ascending modified date]]
    by_modified_desc, [[Sort by descending modified date]]
-   last [[Sentinel (helper) value, not used.]]
+   last [[Sentinel value to indicate last enum field during iteration]]
 }
 
 interface Elm.Interface.Fileselector ()

src/lib/elementary/elm_popup.eo

@@ -19,7 +19,7 @@ enum Elm.Popup.Orient
    top_right, [[Popup should appear in the top right of parent.]]
    bottom_left, [[Popup should appear in the bottom left of parent.]]
    bottom_right, [[Notify should appear in the bottom right of parent.]]
-   last [[Sentinel value, don't use.]]
+   last [[Sentinel value to indicate last enum field during iteration]]
 }
 
 

src/lib/elementary/elm_web.eo

@@ -11,7 +11,7 @@ enum Elm.Web.Zoom_Mode
    manual = 0, [[Zoom controlled normally by elm_web_zoom_set]]
    auto_fit, [[Zoom until content fits in web object]]
    auto_fill, [[Zoom until content fills web object]]
-   last [[Sentinel value to indicate end]]
+   last [[Sentinel value to indicate last enum field during iteration]]
 }
 
 class Elm.Web (Elm.Widget)