Added nfs4 support for linux
Add support for recent 4.0-only configurations
fix typos in comments
reduce switch statement
Add support for monitoring lm_sensors' "power" sensors

The patch shall probably be extended to include additional sensor names in
future. My servers, however, use "power1" for all of the readings, so I'm not
making that change now.
Add postgresql writer option to skip older values.
Fix for number of nfs40 client fields on linux >=3.5
add more innodb metrics
submit mysql_bpool_bytes as gauge
Added support for the last two additional columns in add-linux-io-time
missed the output_name
configure: add varnish4 presence detection
varnish: bare minimum changes to support varnish4
varnish: adapt to metrics renames & deprecations in varnish4

Summary of changes:
- connections: "accepted" & "dropped" are now found in the session section
- dirdns: doesn't exist in varnish 4 anymore
- objects: "n_obj*" were removed from varnish 4
- ban: "obj", "req" & "completed" bans were added. As a lot of new
  "tested" metrics are available, so we only collectd the overall total
  now
- session: metrics from "connections" and "threads" categories were
  moved here
- struct: "n_sess*" were removed
- totals: new, more detailed *bytes metrics were made available
- threads: new metrics were made available. "queued" was moved the
  session section.
varnish: add a couple of metrics available both in V3 & V4
varnish: monitor 2 purge-relatad metrics added in V4
varnish: monitor VSM usage stats, made available in V4
varnish: correct an erroneous type

Affects Varnish 3 only.
varnish: manpage & example cleanup

Consitently alphabetically ordered options and ensured all version
limitations are mentioned.
varnish: add some detail & references to manpage