FIX: trailing whitespace
use std::list<> instead of next ptr
detect legacy libcvmfs version
add cvmfs_context* to cvmfs_filesystem struct
refactor cvmfs_activate_filesystem() sanity checks
FIX: indentation
reuse previously attached repos
add compatibility wrappers for cvmfs functions
use compatibility wrappers
add --cvmfs-config=<> to parrot arguments
FIX: include libcvmfs.h as a library
read global cvmfs configuration
remove useless warning
Merge branch 'feature-multi_repo' of github.com:reneme/cctools into reneme-feature-multi_repo

This adapts the Parrot CernVM-FS module to work with a newer version of
libcvmfs that is going to come in a future version of CVMFS. Its main
advantage is the support for multiple CVMFS repositories through a
single instance of libcvmfs. Please see this branch in the CVMFS git
repository.

The parrot module detects the version of libcvmfs at compile time and
enables the enhancements accordingly. Please note, that I needed to
change the configuration scheme of libcvmfs, thus current installations
need to be adapted. Mainly I separated global configuration (like cache
directory, logging, ...) from repository configuration (repo name, URL,
proxy, ...).

When using multiple repositories, they share one common cache. However,
this comes with the cost of dropping cache quota management for the
moment. The quota management is done globally in CVMFS thus repositories
would step on each others feet. Therefore I decided to disable it
entirely resulting in an ever growing cache.

Unfortunately, I don't have the possibility to verify the proper
functionality. I ran some basic tests (like compiling the linux kernel
through parrot - installed in the sft.cern.ch repository). Maybe you
have better means to test it?

Main things done:

detect libcvmfs version through the macro LIBCVMFS_VERSION (the new
libcvmfs defines it to 2, the old one doesn't define it at all)
add --cvmfs-config=<global config> switch to parrot_run
replace custom linked list of struct cvmfs_filesystem by
std::list
wrap calls to libcvmfs into thin compatibility functions
(#ifdef into libcvmfs 1 or 2 library calls)
adapt initialization code in
cvmfs_activate_filesystem(),
cvmfs_filesystem_create() and
cvmfs_filesystem::createMatch() to new libcvmfs
semantics
remove trailing whitespace (Sublime did that for
me ;-) )

Conflicts:
	parrot/src/pfs_main.cc