Add global .gitignore file
Ignore general output files: object files, libraries, archives,
temporary files.
Signed-off-by: 
Razvan Deaconescu <razvan.deaconescu@upb.ro>
Ignore general output files: object files, libraries, archives,
temporary files.
Signed-off-by: Razvan Deaconescu <razvan.deaconescu@upb.ro>