[RFC] LTTV: New resource viewer module

We, at Polytechnique Montreal, are currently working on a new graphical
plugin for LTTV that shows the usage of several system resources through
time. Resources include block devices (reads, writes), irq handlers and
cpus (busy, idle, in irq, in trap).

Screenshots are available at:

http://ltt.polymtl.ca/rvshots/

Image resource1.png shows a copy operation from a cdrom drive (Block
(22,0) to a hard disk (Block (3,0)). Image resource2.png shows a
2-processor compilation server with a compilation in progress.

For block devices, blue=reading, red=writing. For CPUs, gray=idle,
white=busy in process context, red=busy in irq handler, yellow=busy in
trap handler. For irqs, red=running handler.

A first version is available in the latest LTTV release (0.8.84).
However, tracing block device usage requires patches both to the kernel
and to LTTV that have not been released yet.

Trying the module requires loading the libresourceview.so library
through the "Plugins" menu or running lttv with the -m resourceview
option. It can then be displayed by choosing "Insert Resource Viewer"
from the "Tools" menu.

Please keep in mind that this is work in progress. Fixes for a few
issues are already queued for the next LTTV release.

Comments are welcome.

pmf