Add two new data types: DCOUNTER and DDERIVE, which resemble
COUNTER and DERIVE, but take double precision floating point
number as an argument. Like it or not, the world as we know it
is not described by integer numbers, not even the real numbers,
it's complex amplitudes, folks. But well, we don't onserve
amplitudes directly, so real numbers are the closest bet that
we have at the moment.

This is still WiP, documentation is coming.
Merge remote-tracking branch 'upstream/master'

Conflicts:
	src/rrd_create.c
	src/rrd_update.c
Remove utility function rrd_get_double(), it's been replaced
by the rrd_strtodbl().
Don't update pdp_new[] in-place, this is a bad practice from the
error-handling prospective.
Const'ify the last argument of the rrd_strtodbl() properly.
Add some documentation for the DCOUNTER and DDERIVE.
Use "-Wl,--rpath -Wl,$rp" on FreeBSD instead of depreciated
"-R$rp", which is not working anymore with the clang toolchain.
Do a NULL check bit yearlier, before we actually try to deref the
pointer. Otherwise we might segfault in certain conditions.
Modernize for the autoconf 2.69.
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'

Conflicts:
	src/rrd_graph_helper.c
Add dcounter1 regression test script to test DCOUNTER / DDERIVE
ds types.
Add new version 5 of the RRD format to be activated when either
DCOUNTER or DDERIVE data type is requested. This is to provide
useful error output when trying to read new RRDs using old tools.
Undo 409339b1cbed277ff7adb53156fbe9b1abcd3f59 to make travis happy.
Modernize for the autoconf 2.69.
Filter out "NaNs" from the fetch output, we are getting "-nan" on
linux, vs. "nan" on FreeBSD.
Undo 409339b1cbed277ff7adb53156fbe9b1abcd3f59 once again, I should
have waited for the travis to chew it through before re-adding it
again.
/usr/local/bin/bash -> /bin/bash.
Add missing deref.
Skip "fetch" test for the rrdcached-style test. For some reason it
produces lot of unwanted output, which breaks it.