nfs, zfs_arc plugins: Fixed discards qualifiers from pointer target type warn.

kstat_data_lookup() and get_kstat_value() expect char pointers rather than
const char pointers.
nfs, zfs_arc plugins: Make sure to return from non-void function.
Moved files into standard directory structure
Merged Niki's changes to `collectd.h' to trunk/
Fiddling with that autoconf/automake stuff..
RRDs and PID file are now underneath `localstatedir'
Changes debian package to build with the new path settings
Added information about cpufreq to ReadMe and manpage
Corrected the default prefix in `INSTALL'
First version of the users plugin.
Now using utmpx instead of utmp in users.c to be POSIX 1003.1-2001 compliant.
Added checks for `utmpx.h' and `getutxent' to the configure script
Added backwards compatibility to `users.c', so I can use `utmp' too if `utmpx' is not found.
Fixes for the load module (did not work correctly under Solaris)
Updated the manpage (added multicast routing information and fixed typos)
Improved the build process a bit..
Bumped version to 3.5.alpha0
Added FreeBSD support to the cpu module
Added potential bug
Copied src/utils_debug.[ch] from quota-branch to trunk
Copied src/utils_mount.[ch] from quota-branch to trunk