Greek caps (#1283)

* Support Greek capital letters

Supports Greek letters ΑΒΕΖΗΙΚΜΝΟΡΤΧ.

Resolves issue #1282.

test/katex-spec.js

@@ -2991,6 +2991,11 @@ describe("Unicode", function() {
         expect("£¥ðℂℍℑℓℕ℘ℙℚℜℝℤℲℵℶℷℸ⅁∀∁∂∃∇∞∠∡∢♠♡♢♣♭♮♯✓°\u00b7").toParse();
     });
 
+    it("should build Greek capital letters", function() {
+        expect("\u0391\u0392\u0395\u0396\u0397\u0399\u039A\u039C\u039D" +
+                "\u039F\u03A1\u03A4\u03A7").toBuild();
+    });
+
     it("should parse arrows", function() {
         expect("←↑→↓↔↕↖↗↘↙↚↛↞↠↢↣↦↩↪↫↬↭↮↰↱↶↷↼↽↾↾↿⇀⇁⇂⇃⇄⇆⇇⇈⇉").toParse();
     });