Help: Minor text clarifications in cmake-language(7) manual

Clarify definitions of `bracket_open` and `bracket_close` productions.

In note about unquoted arguments containing unescaped double quotes,
provide examples of how they can be written as quoted arguments.

Also clarify location of nested calls supported by variable function
scope.

Suggested-by: Дилян Палаузов <dilyan.palauzov@aegee.org>

Help/manual/cmake-language.7.rst

@@ -183,18 +183,18 @@ same length:
 
 .. productionlist::
  bracket_argument: `bracket_open` `bracket_content` `bracket_close`
- bracket_open: '[' '='{len} '['
- bracket_content: <any text not containing a `bracket_close`
-                :  of the same {len} as the `bracket_open`>
- bracket_close: ']' '='{len} ']'
+ bracket_open: '[' '='* '['
+ bracket_content: <any text not containing a `bracket_close` with
+                :  the same number of '=' as the `bracket_open`>
+ bracket_close: ']' '='* ']'
 
 .. raw:: latex
 
    \end{small}
 
-An opening bracket of length *len >= 0* is written ``[`` followed
-by *len* ``=`` followed by ``[`` and the corresponding closing
-bracket is written ``]`` followed by *len* ``=`` followed by ``]``.
+An opening bracket is written ``[`` followed by zero or more ``=`` followed
+by ``[``.  The corresponding closing bracket is written ``]`` followed
+by the same number of ``=`` followed by ``]``.
 Brackets do not nest.  A unique length may always be chosen
 for the opening and closing brackets to contain closing brackets
 of other lengths.
@@ -334,6 +334,8 @@ For example:
  beginning of an unquoted argument, and are treated as part of the
  content.  For example, the unquoted arguments ``-Da="b c"``,
  ``-Da=$(v)``, and ``a" "b"c"d`` are each interpreted literally.
+ They may instead be written as quoted arguments ``"-Da=\"b c\""``,
+ ``"-Da=$(v)"``, and ``"a\" \"b\"c\"d"``, respectively.
 
  Make-style references are treated literally as part of the content
  and do not undergo variable expansion.  They are treated as part
@@ -514,7 +516,7 @@ Function Scope
  create commands that, when invoked, process the recorded commands
  in a new variable binding scope.  A variable "set" or "unset"
  binds in this scope and is visible for the current function and
- any nested calls, but not after the function returns.
+ any nested calls within it, but not after the function returns.
 
 Directory Scope
  Each of the `Directories`_ in a source tree has its own variable