libwebsockets

lejp bring into lws

lejp is already in lws as part of lwsws.  However it's too generally useful
to just put directly in lwsws, it will lead to multiple copies of the source
in differet subprojects.

This moves it directly into lws, lwsws now gets it from there.

Like lwsws, by default at cmake it is disabled.  Selecting LWS_WITH_LWSWS now
selects LWS_WITH_LEJP and you can set that at cmake individually as well.

Signed-off-by: Andy Green <andy@warmcat.com>