configure: Warn about deprecated hosts

configure: Warn about deprecated hosts

We plan to drop support in a future QEMU release for host OSes
and host architectures for which we have no test machine where
we can build and run tests. For the 2.9 release, make configure
print a warning if it is run on such a host, so that the user
has some warning of the plans and can volunteer to help us
maintain the port if they need it to continue to function.

This commit flags up as deprecated the CPU architectures:
 * ia64
 * sparc
 * anything which we don't have a TCG port for
   (and which was presumably using TCI)
and the OSes:
 * GNU/kFreeBSD
 * DragonFly BSD
 * NetBSD
 * OpenBSD
 * Solaris
 * AIX
 * Haiku

It also makes entirely unrecognized host OS strings be
rejected rather than treated as if they were Linux (which
likely never worked).

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1490106717-9542-1-git-send-email-peter.maydell@linaro.org