Add LSL support from Zai Lynch

Author copyright statement:
Linden Scripting Language (LSL) highlighter for JOE
by Zai Lynch - https://wiki.secondlife.com/wiki/User:Zai_Lynch
is a modification of the PASCAL highlighter by Michael Van Canneyt
Last update: March 26th 2009
Since JOE is released under GPL 1, this file is also released as GPL 1
Merge pull request #9 from iarna/lsl-support

Add LSL support from Zai Lynch