Add 'registered' and 'trademark' to mapPrivateUseChars (bug 925985)

Fixes the missing trademark (&#x2122;) in: https://bugzilla.mozilla.org/show_bug.cgi?id=925985.

Note that I originally found this issue while reading: https://partners.adobe.com/public/developer/en/font/5015.Type1_Supp.pdf. In that file there are both trademark and registered (&#x00AE;) characters missing, which is why they are both included in this PR.