Fix build for debian linux 32-bit and people who don't have luajit installed globally
Add useful usage string back in
add initial gyp support
Squashed 'tools/gyp/' content from commit 736e7ee

git-subtree-dir: tools/gyp
git-subtree-split: 736e7ee0fcaca126382d1abd0a2707ca7b29c679
Merge commit '486e6e4f03125e126056695e846fdd5d83021f37' as 'tools/gyp'