int chmod( const char *filename, int permiss)

	- prototype in io.h, also include stat.h

	- changes access mode of file according to mask given by permiss,
	  where permiss is:

			S_IWRITE
			S_IREAD
			S_IWRITE | S_IREAD

	- returns 0 if OK
		 -1 with errno set to ENOENT or EACCES