rfc4251string: don't store the length
rfc4251string: implement name-list (as vector<string>)
improve debug mode

also clean up socket in debug mode
also exit when catching SIGINT
remove unneeded namespace qualification, ADL works here
Makefile: reset version.h on clean when in git
rfc4251string: add length checks
use more uniform initialization

std::string(1, <some char>) becomes std::string{<some char>}

also fix accidental use of ssize_t instead of size_t with gmp

This yielded two warnings (-Wnarrowing) where a size_t is used to initialize
an rfc4251uint32, they were fixed with a cast.
remove declarations for default copy and move
remove some inline specifiers

* from functions defined inside the struct
* from non-trivial functions
Makefile: add libstdc++ to LDFLAGS
reorganize import code for name-list and mpint

reuse some common parts
add basic bash-completion

escaping of some special chars is not handled yet
move mpint/mpz conversion into separate file

these functions need linking against libgmp