Add support for nesC

nesC is an embedded systems language. It it is a stable product (~10
years old) primarily used for TinyOS, an embedded operating system.
Development has recently moved to github (https://github.com/tinyos/nesc).

Pygments has now pulled the nesC lexer as of 2013/5/6:
  https://bitbucket.org/birkenfeld/pygments-main/pull-request/166/

Please let me know if I need to do anything else / add more information.