SBCL-style Unicode support: one character = one Unicode codepoint.

Allow one JSCL "character" object to be a surrogate pair (length-2 JS
string).
Unicode-aware implementations of most of the Characters dictionary.
CHAR-NAME and NAME-CHAR, for ASCII names.
Character comparisons, case sensitive.
Character comparisons, case insensitive.
Character case predicates.
Extend DIGIT-CHAR-P to include all HexDigit characters.
Fixing tabs/spaces.  (Oops.)
Merging from upstream.
Merge pull request #112 from kengruven/master

Character functions