like we have on other platforms. Move savectx() to <machine/pcb.h>.
A lot of files got these MD prototypes through the indirect inclusion
of <machine/cpu.h> and now need to include <machine/md_var.h>. The
number of which is unexpectedly large...
osf1_misc.c especially is tricky because szsigcode is redefined in
one of the osf1 header files. Reordering of the include files was
needed.
linprocfs.c now needs an explicit extern declaration.
Tested with: LINT
3e25ce2310