Nmap detection

[ilyaglow]

Related lines in the nmap sources:

• https://github.com/nmap/nmap/blob/master/scan_engine_raw.cc#L300
• https://github.com/nmap/nmap/blob/master/scan_engine_raw.cc#L449
• https://github.com/nmap/nmap/blob/master/scan_engine_raw.cc#L466
• https://github.com/nmap/nmap/blob/master/scan_engine.h#L290

Depends on #4