tools+stubdom: install under /usr/local by default.

tools+stubdom: install under /usr/local by default.

Now that the hotplug scripts have been fixed to remove hardcoded paths lets
try this again. From 26470:acaf29203cf9:

	This is the defacto (or FHS mandated?) standard location for software
	built from source, in order to avoid clashing with packaged software
	which is installed under /usr/bin etc.

	I think there is benefit in having Xen's install behave more like the
	majority of other OSS software out there.

	The major downside here is in the transition from 4.2 to 4.3 where
	people who have built from source will innevitably discover breakage
	because 4.3 no longer overwrites stuff in /usr like it used to so they
	pickup old stale bits from /usr instead of new stuff from /usr/local.

	Packages will use ./configure --prefix=/usr or whatever helper macro
	their package manager gives them. I have confirmed that doing this
	results in the same list of installed files as before this patch was
	applied.

	The hypervisor remains in /boot/ and there is no intention to move it.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>