Added a .gitignore file.

.pro.user files are now ignored, as are .o files.
Soundbench now compiles on Mac OS.

Note: The CPU meter does not function as it would on Windows and Linux.
Fixed a bug in which compiling without the JACK libraries would simply
not work.
Fixed a redefinition in the playback sample table.
Soundbench.pro.user is now explicity ignored.