Random bug fixes in Utah Lites Release 1.1.u2

• Integrated Jukka Partanen's (jtp@cs.hut.fi) mmap fix that allows NetBSD and FreeBSD shared libraries to work.

• The e_bsd_sigprocmask emulator entry point should have only two parameters, not three (the 4.4 system call interface is not the same as the documented user interface). This bug caused the old signal mask to always be returned as zero. This was only fixed in the generic Lites sysent table. Other emulation tables were left alone since we didn't know if this is a correct change for them.

• Integrated a variant of Ian Dall's (dall@hfrd.dsto.gov.au) signal mask fix. This bug caused the signal mask to be improperly restored after a signal handler in some cases.

• Commented the race condition caused by forcibly delivering a signal from the server to a running process. TODO: Find and fix this bug.

• Integrated some filesystem clustering fixes that postdate 4.4-Lite. TODO: Update the filesystem code to 4.4-Lite-2 level; there are still more cluster related fixes in that code.

• Hack to make ensure block device ioctls always work.

• Implement /dev/zero.

• Commented mutex_holder_assert out of the MASTER.h file to avoid ``lock holder == 0'' assertion-failure panics when Lites is compiled with the DEBUG option. TODO: Find and fix this bug.

• Put a sequence number sanity check in the port object code. If a message came in with a bogus sequence number (e.g., from a not quite working new RPC system :-), the server could hang forever.

• Fixed a port reference underrun problem in the port object code. In some situations the extra_urefs field would get out of sync with the actual reference count causing mach_port_mod_refs to fail resulting in an assertion-failure panic.