add 21:9 and 9:16 to ConfAspectRatio in _fallback

This adds choices for 21:9 (Ultrawide) and 9:16 (widescreen display in
portrait mode) to the _fallback theme.  Previously, users would have to
manually edit Preferences.ini to achieve either of these.

Since "21:9" is the common marketing term for what is actually 64:27,
I've slightly extended GenChoices() in ConfAspectRatio() to use a "name"
string from the winFracs table is one is provided. If not, the original
behavior of generating user-facing choices from the raw values is
preserved.

See: https://wikipedia.org/wiki/21:9_aspect_ratio

I updated the global AspectRatios table in _fallback/02 Utilities.lua to
match.

Themes/_fallback/Scripts/02 Utilities.lua

@@ -329,13 +329,15 @@ end
 
 -- supported aspect ratios
 AspectRatios = {
-	ThreeFour   = 0.75,		-- (576x760 at 1024x768; meant for rotated monitors?)
-	OneOne      = 1.0,		-- 480x480  (uses Y value of specified resolution)
-	FiveFour    = 1.25,		-- 600x480 (1280x1024 is a real use case)
-	FourThree   = 1.33333,	-- 640x480 (common)
-	SixteenTen  = 1.6,		-- 720x480 (common)
-	SixteenNine = 1.77778,	-- 853x480 (common)
-	EightThree  = 2.66666	-- 1280x480 (two monitors)
+	ThreeFour    = 0.75,    -- (576x760 at 1024x768; meant for rotated monitors?)
+	OneOne       = 1.0,     -- 480x480  (uses Y value of specified resolution)
+	FiveFour     = 1.25,    -- 600x480 (1280x1024 is a real use case)
+	FourThree    = 1.33333, -- 640x480 (common)
+	SixteenTen   = 1.6,     -- 720x480 (common)
+	SixteenNine  = 1.77778, -- 853x480 (common)
+	EightThree   = 2.66666, -- 1280x480 (two monitors)
+	TwentyOneNine= 2.37,    -- 1138x480 (Ultrawide)
+	NineSixteen  = 0.5625,  -- 480x720  (16:9 widescreen as portrait display)
 }
 
 function WideScale(AR4_3, AR16_9)