Ensure proper highlighting of legal Clojure symbols

This patch fixes highlighting of Clojure symbols that involve characters
such as "'", "#", and ":".

Previously a symbol like `super:hero` would incorrectly treat the
":hero" portion of the symbol as a clojureKeyword. Also if a symbol
contained a "'" or "#" character it would be highlighted. In addition to
this observation, if the symbol contained a keyword following the "'" or
"#" character, it would be highlighted. So the symbol `burger'time`
would produce the synIDs clojureSexp, clojureQuote, and clojureMacro
respectively.
Place boundaries around keywords
Improve symbol highlighting, extend clojureAnonArg
Minor correction to clojureSymbol
Allow multibyte characters in clojureSymbol
Merge branch 'noprompt-syntax-bugfixes'

Closes #17.

Creates new syntax match group "clojureSymbol" which remains unlinked to
a highlight group.

* noprompt-syntax-bugfixes:
  Allow multibyte characters in clojureSymbol
  Minor correction to clojureSymbol
  Improve symbol highlighting, extend clojureAnonArg
  Place boundaries around keywords
  Ensure proper highlighting of legal Clojure symbols
Fix clojureAnonArg so %21-%29 are not highlighted
Use \d \o and \x char classes when possible
Allow infix % in clojureSymbol
Use snake_case for s:radix_chars