patch 8.1.1683: dictionary with string keys is longer than needed

Problem:    Dictionary with string keys is longer than needed.
Solution:   Use *{key: val} for literaly keys.

runtime/doc/eval.txt

@@ -58,7 +58,9 @@ List		An ordered sequence of items, see |List| for details.
 
 Dictionary	An associative, unordered array: Each entry has a key and a
 		value. |Dictionary|
-		Example: {'blue': "#0000ff", 'red': "#ff0000"}
+		Examples:
+			{'blue': "#0000ff", 'red': "#ff0000"}
+			*{blue: "#0000ff", red: "#ff0000"}
 
 Funcref		A reference to a function |Funcref|.
 		Example: function("strlen")
@@ -477,8 +479,14 @@ only appear once.  Examples: >
 A key is always a String.  You can use a Number, it will be converted to a
 String automatically.  Thus the String '4' and the number 4 will find the same
 entry.  Note that the String '04' and the Number 04 are different, since the
-Number will be converted to the String '4'.  The empty string can be used as a
-key.
+Number will be converted to the String '4'.  The empty string can also be used
+as a key.
+						*literal-Dict*
+To avoid having to put quotes around every key the *{} form can be used.  This
+does require the key to consist only of ASCII letters, digits, '-' and '_'.
+Example: >
+	let mydict = *{zero: 0, one_key: 1, two-key: 2, 333: 3}
+Note that 333 here is the string "333".  Empty keys are not possible here.
 
 A value can be any expression.  Using a Dictionary for a value creates a
 nested Dictionary: >