Don't version auto-generated documentation.

That's an antipattern. Instead, add Source/Docs/* to .gitignore, and
let people build the docs themselves. This keeps them from getting out
of sync with the source tre and from cluttering up the diffs.

Signed-off-by: Marti Bolivar <mbolivar@leaflabs.com>
Add cscope files to .gitignore.

Ignoring these allows running cscope-indexer without git status
complaining.

Signed-off-by: Marti Bolivar <mbolivar@leaflabs.com>
Add some Emacs files to .gitignore.

This ignores Emacs autosave files and any directory-local variable
files.

Signed-off-by: Marti Bolivar <mbolivar@leaflabs.com>