Correctly detect OpenType font files with CFF data

Fixes 5334.
Fixes 215.
Fixes https://bugzilla.mozilla.org/show_bug.cgi?id=1125614.

According to the specification, http://www.microsoft.com/typography/otspec/otff.htm, OpenType font files with CFF data should have `OTTO` in the header.

src/core/fonts.js

@@ -2572,8 +2572,6 @@ var Font = (function FontClosure() {
     if (subtype === 'CIDFontType0C' && type !== 'CIDFontType0') {
       type = 'CIDFontType0';
     }
-    // XXX: Temporarily change the type for open type so we trigger a warning.
-    // This should be removed when we add support for open type.
     if (subtype === 'OpenType') {
       type = 'OpenType';
     }
@@ -3980,7 +3978,8 @@ var Font = (function FontClosure() {
       var isTrueType = !tables['CFF '];
       if (!isTrueType) {
         // OpenType font
-        if (!tables.head || !tables.hhea || !tables.maxp || !tables.post) {
+        if (header.version === 'OTTO' ||
+            !tables.head || !tables.hhea || !tables.maxp || !tables.post) {
           // no major tables: throwing everything at CFFFont
           cffFile = new Stream(tables['CFF '].data);
           cff = new CFFFont(cffFile, properties);

test/pdfs/.gitignore

@@ -113,6 +113,7 @@
 !issue4722.pdf
 !issue4800.pdf
 !issue4801.pdf
+!issue5334.pdf
 !issue5549.pdf
 !issue5475.pdf
 !issue5481.pdf

test/test_manifest.json

@@ -421,6 +421,13 @@
        "rounds": 1,
        "type": "load"
     },
+    {  "id": "issue5334",
+       "file": "pdfs/issue5334.pdf",
+       "md5": "5575020f37f6e5b3c43b8183bf7f96ae",
+       "rounds": 1,
+       "link": false,
+       "type": "eq"
+    },
     {  "id": "bug850854",
        "file": "pdfs/bug850854.pdf",
        "md5": "346a034a80120d123b9fefc42bcb11da",