Bring gotd and gitwrapper closer to how libraries are detected.

Include listen.c; make it portable.

Move gotd_find_uid_connection_limit() from listen.c into parse.y and remove listen.c from the list of source files required by gitwrapper.

ok op@

Simply the SHA detection by not predicating on libcrypto, but instead checking individual header files.

Remove sha1.h as this is found portably across systems.

In preparation for wide sha256 support; stsp@ agrees. Change done mechanically with find . -iname \*.[cy] -exec sam {} + X ,x/<sha1\.h>/i/\n#include <sha2.h>

i.e. "listen: listen: shutting down" -> "listen: shutting down" the procname is already prepended by vlog() ok jamsek

Allow administrators to tweak the default authentication and request timeouts if needed, and to tweak the limit of concurrent connections for specific user accounts. with several tweaks from and ok op@

For now the limit is set at compile-time. It will become configurable via gotd.conf soon. ok op@

The listen process now communicates the client UID/GID to the parent, and the auth process verifies this on behalf of the parent. This allows us to remove the "unix" pledge promise from the parent, removing parent access to syscalls such as listen() and accept() in the AF_UNIX domain. ok tracey@ op@

ok op@