generate Stan keywords directly from manual
new keyword lists for Stan 2.0.1
update to use new keyword lists

Updates functions and keywords to Stan 2.0.1
Add file to check syntax highlighting
Updated to Stan 2.0.1 language

- added code to generate keywords directly from the manual
- added a file to text syntax highlighting
added cholesky_factor_cov snippet
added distribution snippet
remove unused / unsupported code

Some code initially useful for functions to compile the
Stan model directly. Not used since I think it is better
to specify all this in a Makefile.
update compilation-regexp patterns

- fixed pattern
- defined in a more idiomatic manner
name of stanc executable conditional on OS