source-highlight: 3.1.6 -> 3.1.7

From NEWS file (version 3.1.7):

  * fixed compilation bugs in MacOsX systems (thanks to
    Trevor Spiteri)
  * language definition for Lilypond (thanks to Federico Bruni)
  * language definition for R statistics programming language
  * language definition for ISLISP (thanks to Christian Jullien)
  * improved Erlang definition file (thanks to Erik Søe Sørensen)
  * new output format: ESC 256 ascii code (thanks to
    Xavier-Emmanuel Vincent).

(It still needs boost 1.53 for all tests to pass.)