Add support for \aa, \AA, \lq, \rq, \lbrack, \rbrack (#1069)

* Add support for \aa, \AA, \lq, \rq, \lbrack, \rbrack

The lack of \aa and \AA was reported in #1066.  Added these
via simple macros, with supporting tests.  Also add \lq, \rq,
\lbrack, \rbrack as aliases for "`", "'", "[", "]" which were
in the same area of latex.ltx.

* removed duplicate comment

src/macros.js

@@ -96,12 +96,27 @@ defineMacro("\\TextOrMath", function(context) {
 });
 
 //////////////////////////////////////////////////////////////////////
-// basics
+// Grouping
+// \let\bgroup={ \let\egroup=}
 defineMacro("\\bgroup", "{");
 defineMacro("\\egroup", "}");
 defineMacro("\\begingroup", "{");
 defineMacro("\\endgroup", "}");
 
+// Symbols from latex.ltx:
+// \def\lq{`}
+// \def\rq{'}
+// \def\lbrack{[}
+// \def\rbrack{]}
+// \def \aa {\r a}
+// \def \AA {\r A}
+defineMacro("\\lq", "`");
+defineMacro("\\rq", "'");
+defineMacro("\\lbrack", "[");
+defineMacro("\\rbrack", "]");
+defineMacro("\\aa", "\\r a");
+defineMacro("\\AA", "\\r A");
+
 // Unicode double-struck letters
 defineMacro("\u2102", "\\mathbb{C}");
 defineMacro("\u210D", "\\mathbb{H}");

test/katex-spec.js

@@ -2798,6 +2798,12 @@ describe("Unicode accents", function() {
             "\\'y\\\"y}");
     });
 
+    it("should support \\aa in text mode", function() {
+        expect("\\text{\\aa\\AA}").toParseLike("\\text{\\r a\\r A}");
+        expect("\\aa").toNotParse();
+        expect("\\Aa").toNotParse();
+    });
+
     it("should parse combining characters", function() {
         expect("A\u0301C\u0301").toParseLike("Á\\acute C");
         expect("\\text{A\u0301C\u0301}").toParseLike("\\text{Á\\'C}");