[RPL/2] RPL/2 4.1.31

[BERTRAND Joël]

	Hello,

	New RPL/2 release with some fixes. All tools and builtin libraries have
been upgraded. RPL/CAS is fixed to be built with GCC 9.2 without error.

	Multithreading support is improved (and some bugs have been fixed in
SPAWN intrinsic).

	SYSEVAL is modified. Now data sent by stdin in child process are sent
in a special thread (to avoid locking condition in stdin socket). And
when RPL/2 receives a SIGINT signal, it tries to stop child process with
TERM signal. If child process doesn't stop after 10 seconds, RPL/2 sends
KILL signal.

	Best regards,

	JKB