qemu-timer.c: Trim list of included headers

qemu-timer.c was including a lot more headers than it needed to,
presumably for historical reasons. In particular, it included
ui/console.h; this now tries to pull in <pixman.h>, which will
cause a compilation failure in --disable-tools --disable-system
configurations when running "make check" (which builds qemu-timer.c,
even though the linux-user binaries themselves don't need it).

Fix this build failure by trimming down the set of included
headers severely -- we only really need main-loop.h and timer.h.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 1421770600-17525-1-git-send-email-peter.maydell@linaro.org