translate-all: use glib for all page descriptor allocations

Since commit

  b7b5233a "bsd-user/mmap.c: Don't try to override g_malloc/g_free"

the exception we make here for usermode has been unnecessary.
Get rid of it.

Signed-off-by: Emilio G. Cota <cota@braap.org>
Message-Id: <1428610053-26148-1-git-send-email-cota@braap.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
