alsaloop: add libsamplerate-dev build-dep

[Impact statement]
alsaloop, a command-line utility shipped in Oneiric's alsa-utils binary package, does not work because of a missing build-dependency on libsamplerate-dev.

[Development fix] / [Stable fix]
Corrected in r95 of http://bazaar.launchpad.net/~ubuntu-audio-dev/alsa-utils/ubuntu.oneiric/revision/95 and r2558 of http://anonscm.debian.org/viewvc/pkg-alsa?view=revision&revision=2558.

[Test case] (from the original defect report)
----------example from the manpage-----------------
alsaloop -C hw:0,0 -P hw:0,0 -t 50000
No libsamplerate support.
----------example from the manpage-----------------

[Regression potential]
Low - the additional build-dependency only affects (enables) the alsaloop utility.

[Original defect report]
Please add libsamplerate-dev to the build-deps of alsa-utils to make alsaloop actually work

----------example from the manpage-----------------
alsaloop -C hw:0,0 -P hw:0,0 -t 50000
No libsamplerate support.
----------example from the manpage-----------------

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: alsa-utils 1.0.24.2-0ubuntu8
ProcVersionSignature: Ubuntu 3.0.0-12.19-generic-pae 3.0.4
Uname: Linux 3.0.0-12-generic-pae i686
NonfreeKernelModules: nvidia
ApportVersion: 1.23-0ubuntu2
Architecture: i386
Date: Wed Oct 5 23:25:30 2011
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release i386 (20110427.1)
SourcePackage: alsa-utils
UpgradeStatus: Upgraded to oneiric on 2011-10-04 (1 days ago)