Use suspend_hybrid where supported

If a system reports that hybrid suspend is supported, as a result of pm-is-supported --suspend-hybrid then suspend should default to using hybrid suspend. Allow an override via /etc/defaults in case there are systems that report hybrid supported that then don't work.

See this blog posting - http://daniel.hahler.de/use-hybrid-suspend-method-by-default

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: pm-utils 1.4.1-9
ProcVersionSignature: Ubuntu 3.2.0-25.40-generic 3.2.18
Uname: Linux 3.2.0-25-generic i686
ApportVersion: 2.0.1-0ubuntu9
Architecture: i386
Date: Fri Jun 29 19:01:46 2012
InstallationMedia: Ubuntu 10.04 LTS "Lucid Lynx" - Release i386 (20100427.1)
PackageArchitecture: all
ProcEnviron:
 SHELL=/bin/bash
 TERM=xterm
 PATH=(custom, user)
 LANG=en_GB.UTF-8
SourcePackage: pm-utils
UpgradeStatus: Upgraded to precise on 2012-04-15 (75 days ago)