User manual: Replace some graphics

1) Two of the major screen images were replaced to reflect the current
   screen layout with the new features of the profile toolbar.
2) The heart rate button is depicted and desribed.
3) Minute changes to the text of the manual to accompany the above changes.
4) The Uwatec Galileo image is re-inserted in the icons folder. Somewhere
   it got lost.

Signed-off-by: Willem Ferguson <willemferguson@zoology.up.ac.za>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
More cross building stuff

This is all mostly to make my life easier.
I'm not thrilled with the marble changes - as Linus pointed out before the
way we do these "LIBxxxDEVEL" changes is broken as it will still first
link against any library installed in the system. But since I have removed
any globally installed copies of these libraries this actually works for
me and it does help when experimenting with different build options for
the main libraries that we depend on.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Windows cross build: use the correct objdump

This one was silly but took me a while to track down.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Windows out of tree cross build: stage package in correct folder

When doing an out of tree build you don't want to stage the package with
the source but under your current directory. So let's make sure we
distinguish between source and target here... and instead of putting
things into packaging/windows they now end up in staging which is much
more consistent. And to make my life even easier, the installer .exe ends
up in the base dir in which you build the package.

Also, we link statically against libdivecomputer, so don't pack the dll.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>