PEG.js grammar: Extract the |AnyMatcher| rule

This makes the |Primary| rule a bit more tidy. Also, matching the |.|
character really belongs to the lexical part of the grammar, next to
literals and character classes.

spec/parser.spec.js

@@ -561,6 +561,11 @@ describe("PEG.js grammar parser", function() {
 
   /* Digit rules are not tested. */
 
+  /* Canonical AnyMatcher is ".". */
+  it("parses CodeAnymatcher", function() {
+    expect('start = .').toParseAs(oneRuleGrammar({ type: "any" }));
+  });
+
   /* Canonical CodeBlock is "{ code }". */
   it("parses CodeBlock", function() {
     expect('start = "abcd" { code }').toParseAs(actionGrammar(" code "));

src/parser.pegjs

@@ -166,7 +166,7 @@ Primary
     }
   / LiteralMatcher
   / CharacterClassMatcher
-  / "." { return { type: "any" }; }
+  / AnyMatcher
   / "(" __ expression:Expression __ ")" { return expression; }
 
 /* "Lexical" elements */
@@ -394,6 +394,9 @@ DecimalDigit
 HexDigit
   = [0-9a-f]i
 
+AnyMatcher
+  = "." { return { type: "any" }; }
+
 CodeBlock "code block"
   = "{" code:Code "}" { return code; }