allows Linux_base-7 to work properly.

tested on alpha by: gallatin (thanks!)
tested on i386 by: marcel (among others probably)

Approved by:	JKH

-----------------------------

The compatibility code and/or emulators have been updated:

iBCS2 now mostly uses the older syscalls. SVR4 now properly
handles all signals. This has been achieved by using the
new sigset_t throughout the emulator. The Linuxulator has
been severely updated. Internally the new Linux sigset_t is
made the default. These are then mapped to and from the
new FreeBSD sigset_t.

Also, rt_sigsuspend has been implemented in the Linuxulator.
Implementing this syscall basicly caused all this sigset_t
changing in the first place and the syscall has been used
throughout the change as a means for testing. It basicly is
too much work to undo the implementation so that it can
later be added again.

A special note on the use of sv_sigtbl and sv_sigsize in
struct sysentvec:
Every signal larger than sv_sigsize is not translated and is
passed on to the signal handler unmodified. Signals in the
range 1 upto and including sv_sigsize are translated.
The rationale is that only the system defined signals need to
be translated.

The emulators also have been updated so that the translation
tables are only indexed for valid (system defined) signals.
This change also fixes the translation bug already in the
SVR4 emulator.

functions use the new sigset_t and sigaction_t which allows support for more
than 32 signals. Only the lower 32 signals are supported for now.

linux_rt_sigaction, linux_sigaction and linux_signal use linux_do_sigaction
to do the actual work. That way unnecessary redundancy is avoided. The same
has been done for linux_rt_sigprocmask and linux_sigprocmask. They call
linux_do_sigprocmask to do the actual work.

with sa_ when <signal.h> is included. They would conflict with the
upcoming SA_SIGINFO implementation.

Reviewed by:	BDE