Fix warnings suppressors to honor --disable-werror

Fix warnings suppressors to honor --disable-werror

Replace

    #pragma GCC diagnostic ignored FOO
    [Troublesome code...]
    #pragma GCC diagnostic error FOO

by

    #pragma GCC diagnostic push
    #pragma GCC diagnostic ignored FOO
    [Troublesome code...]
    #pragma GCC diagnostic pop

Broken in commit 3f4349d, commit 092bb30, and commit c95e308.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Tested-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 1366113066-1340-1-git-send-email-armbru@redhat.com
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>