the latest version of spin is always
available via:
	http://cm.bell-labs.com/cm/cs/what/spin/

to make the sources compile with the mkfile on plan 9
the following changes were made:

	omitted memory.h from spin.h
	omitted malloc.h from ps_msc.c
	changed /lib/cpp to /bin/cpp in main.c
	simplified non_fatal() in main.c to remove
	use of yychar