Better align headers and data for 'procstat -f' with and without '-C'.

MFC after:	3 days
Sponsored by:	DARPA, AFRL
Allow mappings of memory not previously direct-mapped by the kernel when
calling mmap on /dev/mem and add a handler for the possible userland
machine checks that may result. Remove some pointless and wrong copy/paste
that has been in here for a decade as well.

This results in a /dev/mem with identical semantics to the x86 version.

MFC after:	1 week