This will make things as std::to_string() and other C++ features
work with a modern and supported C++ library.
We package up libc++_shared.so and bump the revision of every C++
using package to make it rebuild against it.
Users who have built C++ using libraries or programs will probably
need to rebuild them if they are linked against Termux-supplied
libraries, as user code was previously linked against gnustl while
the system libraries are now using libc++, and it's not a good idea
to mix C++ standard libraries in a program.
Split ncat (https://nmap.org/ncat/), the netcat implementation from
the nmap project out into it's own package.
Also setup netcat as a symlink to ncat for discoverability and
for users used to netcat.
Closes#162.
