Add highlighting for Igor Pro procedures

Available in pygments since 5ceb7533e214.

Signed-off-by: Thomas Braun <thomas.braun@byte-physics.de>
Change lexer for Emacs Lisp from Scheme to Common Lisp
Merge pull request #1499 from pchaigno/emacs-lisp-lexer

Change lexer for Emacs Lisp from Scheme to Common Lisp
Merge pull request #1376 from t-b/add-igor-pro

Add highlighting for Igor Pro procedures
Add a multitude of Forth file extensions.
Yes, these are all in use.
Add Groff sample.
Update samples.json.
Make test_pedantic accept quotes around extensions.