Add elf.h obj.h dependencies.
 [rsc] --rw-rw-r-- M 489211 glenda sys 479 Nov  7 10:01 sys/src/libmach/mkfile
	/n/sourcesdump/2005/1107/plan9/sys/src/libmach/mkfile:38,44 - 
	/n/sourcesdump/2005/1108/plan9/sys/src/libmach/mkfile:38,44
	  	qobj\
	  	vcodas\
	  
	- HFILES=/sys/include/mach.h
	+ HFILES=/sys/include/mach.h elf.h obj.h
	  
	  CFILES=${FILES:%=%.c}