[PATCH] make INSTALL binary in Makefile configurable via make variable

On Solaris machines gnu install called ginstall

<JC> Editorial notes.  I've also changed it to use $(COPTS), $(prefix),
and $(bin) because I always get confused without compiling it with -O1
when I single step in gdb.  The default is left as Linus shipped.

Date:	Sat, 7 May 2005 10:41:54 +0200
Signed-off-by: Thomas Glanzmann <sithglan@stud.uni-erlangen.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>