BFQ and related stuff on disk scheduling

BFQ-v3r2 for 2.6.38, 2.6.39, 3.0, 3.1 and 3.2

These are the changes with respect to v3r1:

• . Latency improvement: low-bw async queues are now better identified.
• . Bugfix: added a forgotten condition that prevents weights of low-bw async queues from being raised when low_latency is off.

For kernels version lower than 3.2, our tests confirmed a further latency reduction with respect to v3r1. We have been told about a timeout problem during login to Gnome 3.2. We have not yet investigated this problem (but are going to).

As usual, Arianna has prepared patches for every possible transition. The patchsets and the incremental patches can be downloaded here.