. if there is no memory there, it's not writable; this
check bug by the shared memory's writable() method causes
pagefaults not to be handled at all in certain situations,
triggering an assert() in pt_writemap()
. added some assert()s to catch this and similar situations
in the future
Change-Id: Ife89bfab4f9a3aa7bf4e33dfb0b13b89dcd5bb94
449ed17833