This replaces the old testtone patch from the days of yore with
Alexandre's new version which looks less boring and also offers some
useful new functionality.

Fixed some typos and minor grammatical errors in the comments, while
also reducing the wall of text at the top, so that the patch (which is
substantially larger than the old one) requires a little less precious
screen real-estate. I think that removing some of the audio/MIDI
configuration hints there doesn't do much harm since that information is
also in the instructions subpatch, as well as being discussed at length
in the Pd manual and the "Meet the Cat" tutorial.

This reverts commit cde4f4f3.

Remove some legacy Tcl/Tk code. Also make sure that image_save doesn't
add the gop-spill flag unless it's really needed, in order to maintain
compatibility with vanilla ggee/image.

Make sure that fiddle~ et al are installed in their proper
subdirectories like on the other platforms, and that we don't overwrite
the PDDP docs in 5.reference with vanilla help patches of the same
name.

Made the fiddle~ message callbacks and sigfiddle_new static, otherwise
instantiation would crash because of a bogus NULL class pointer
(although sigfiddle_class is surely initialized, otherwise sigfiddle_new
could never be called in the first place).

The other stuff in pd/extra seems to be fine, all methods there are
static already, but I haven't checked all the externals.

Observed on Arch with gcc 14.2.1 20240910, Mac and Windows builds seem
to be fine. To me this looks like a compiler or linker bug for that
specific gcc version.  (Come on, Arch, are we now getting compiler
versions from git that haven't been released yet and presumably still
need testing? Who thought that this would be a good idea?)

Updated the source once more to the latest version of the t_vinlet data
structure and initialization code from g_io.c which changed with the
multi-channel backport.

NOTE: This object lacks the message-forwarding of the new inlet~ object
introduced in Pd 0.51. It's also a maintenance burden because of the
amount of code it pulls from g_io.c. Thus the code either needs to be
refactored to facilitate using the required parts from the core
(including message forwarding), or this object should be considered for
removal from moonlib in the future.

This reverts commit 6c726f07.

Rename 25.intelligent-patching.pd to a proper -help patch so that it
appears in the index.

Also renamed snake-tilde-help.pd -> snake~-help.pd.

Replace some really outdated tests for EXTERN_STRUCT. Also added some of
Christof Ressi's improvements to the CLASS_MAINSIGNALIN macro (the
offsetof bit, but not the STATIC_ASSERT bit) to get rid of some gcc
warnings. See: https://github.com/pure-data/pure-data/commit/5b0e0a64

See: https://github.com/pure-data/pure-data/commit/46c2a342

This one change is inconsequential since it's just a demo object that
doesn't actually get compiled, but we should also have the examples
use the correct code.

This adds some features that purr-data still lacked:
- multi-channel support (0.54)
- pd fast-forward support (0.53)

This changeset is quite large, but fortunately pd-l2ork just recently
backported these features from vanilla Pd, so thanks are due to
MovementGH and Ico Bukvic again. See:
https://github.com/pd-l2ork/pd-l2ork/pull/53
https://github.com/pd-l2ork/pd-l2ork/commit/be5183c2
https://github.com/pd-l2ork/pd-l2ork/commit/6fd93d21

Please note that I pulled g_io.c straight from vanilla instead (see the
previous commit), since pd-l2ork currently lacks some vanilla features
that were already added in purr-data.

This adds multi-channel support.

We pull this one straight from vanilla, since pd-l2ork currently lacks
some updates (resampling, inlet~ message forwarding) that purr-data
already ported a while ago.

Revert the changes to m_private_utils.h in rev. eac22a49.
Added the required -DPD_INTERNAL compilation flag in configure.ac.