Fix typos
Add support for the GDScript language

References:
* https://github.com/okamstudio/godot/wiki/gdscript
* http://www.godotengine.org/

Some projects using it:
* https://github.com/okamstudio/godot
* https://github.com/Qwertie-/Godot-games

My motivation for adding it: To disambiguate these .gd
files from GAP .gd files.
Update samples.json
Generate samples before build
Merge pull request #1525 from fingolfin/typos

Fix typos
Merge pull request #1533 from github/travis-samples

Generate samples before build
Merge pull request #1529 from fingolfin/godot

Add support for the GDScript language
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.