print the address of the "non-MAP_STACK stack", so it can be compared
against failure reported in dmesg (hmm, is it time to delete those fault
messages?)

Add stackpivot asm for ppc and ppc64 regress test.

Also tweak the pagefault test to work better on arches
that do not modify the stack pointer on return.

Fix test when using malloc_conf=J
ok otto@

Add a test for stack pivots that trigger page faults.

"Regress is always open for commits" @deraadt