Adds a C library alternative to the ircbot nudge script.

This allows for more secure and stable transmission on Linux, but you might see some improvements on Windows too.
Code lies in (confusingly) lib/src.
nudge.c should be compiled to lib/nudge.[dll/so] and be linked against netutil.c.

There's some horribly hacky code in nudge.c to assemble pickled data, but it's probably the fastest way that's still safe.

Signed-off-by: Mloc-Argent <colmohici@gmail.com>
Merge pull request #4526 from Mloc/bs12-libnudge

Adds a C library alternative to the ircbot nudge script.