Until now if the user pressed Control+C whilst the program was cleaning up (for example waiting for pending packets) the program would die inmediately. This patch renames  the globals control_c_pressed and control_c_pressed_again to much clearer tx_done and rx_done. It also adds propper handling of control_c count handling in the handler itself as a result the wait will now only be cancelled when pressing control+c a second time during the program life instead of on the first control+c if the user pressed it when we are already doing the scan.

We introduce the --nostatus parameter which allows disabling the printing of status updates.
Aside, we allow for reenabling them using the --status parameter

Fix build failure with GCC 5

Patch applied in Debian to solve FTBFS with the GCC's new
version. The original bug report is available here:
- https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=777997

Fix FTBFS on most Debian architectures

Fixes Debian#773786 and enables support on non-ARM,
Non-x86, and kFreeBSD architectures.

JSON names/keys are now quoted to be strings in output

JSON names(keys) output are now strings (double-quoted as per http://tools.ietf.org/html/rfc7158#page-6)