Add .gitignore
Giant commit, but it works!

To use: install input filter (see inputfilter/), and install the app.
Fix build with -werror.
Use an enum instead of an int32 variable for the recording command.
Use a define instead of a variable for the app signature, because the
above changes break building of the input filter
Add a Jamfile to build the input filter within the Haiku build system
Fixed the makefile (not tested, actually)