This complements offset-based resume and playback start funcionality.
The implementation is global on both HWCODEC and SWCODEC.

Basically, if either the specified elapsed or offset are non-zero,
it indicates a mid-track resume.

To resume by time only, set elapsed to nonzero and offset to zero.
To resume by offset only, set offset to nonzero and elapsed to zero.

Which one the codec uses and which has priority is up to the codec;
however, using an elapsed time covers more cases:

* Codecs not able to use an offset such as VGM or other atomic
formats

* Starting playback at a nonzero elapsed time from a source that
contains no offset, such as a cuesheet

The change re-versions pretty much everything from tagcache to nvram.

Change-Id: Ic7aebb24e99a03ae99585c5e236eba960d163f38
Reviewed-on: http://gerrit.rockbox.org/516
Reviewed-by: Michael Sevakis <jethead71@rockbox.org>
Tested: Michael Sevakis <jethead71@rockbox.org>

talk_init() is called by settings_apply() already which is called on boot.
Doing it again means loading the voicefile a second time which isn't necessary.

Change-Id: I4decd16401e63bf87338d3163c99d06d69fe3a3c

When the policy is not set, it'll by default not give the clip buffer away.
Callers of core_alloc_maximum() suffer from this. However, the thumbnail
buffer can be easily freed when needed because nothing needs to be
reloaded from disk when it is reallocated (thumbnail clips are loaded on
demand, when in the file browser). Do this to give core_alloc_maximum() callers
a better chance to succeed with the default talk buffer policy.

Change-Id: I8c0da29c520612ca903f6c930bd7c74ae97eca3b

Change-Id: I13e9a0398efe0dab222f2a9c4f5d9295570e4dfd

This was missed in 22e802e because I didn't realize that hwcodec doesn't
compile pcm_record.c.

Change-Id: I48cd4c2beec0a3d01caf06f2a2ced98be22a3673

This fixes the radioart crash that was the result of buffering.c working
on a freed buffer at the same time as buflib (radioart uses buffering.c for the
images). With this change the buffer is owned by buflib exclusively so this
cannot happen.

As a result, audio_get_buffer() doesn't exist anymore. Callers should call
core_alloc_maximum() directly. This buffer needs to be protected as usual
against movement if necessary (previously it was not protected at all which
cased the radioart crash), To get most of it they can adjust the willingness of
the talk engine to give its buffer away (at the expense of disabling voice
interface) with the new talk_buffer_set_policy() function.

Change-Id: I52123012208d04967876a304451d634e2bef3a33

* Remove explicit tracking of elapsed time of previous track.
* Remove function to obtain auto skip flag.
* Most playback events now carry the extra information instead and
  pass 'struct track_event *' for data.
* Tweak scrobbler to use PLAYBACK_EVENT_TRACK_FINISH, which makes
  it cleaner and removes the struct mp3entry.

Change-Id: I500d2abb4056a32646496efc3617406e36811ec5

Change-Id: I4adb8a152e9b99fcd26d95da7334d7d0cbe2a036

Use generic void * and size_t and make mp3_play_data and its callback
agree on types. Use mp3_play_callback_t instead of prototyping
right in the function call (so it's not so messy to look at). Change
doesn't appear to require plugin API version increment.

Change-Id: Idcab2740ee316a2beb6e0a87b8f4934d9d6b3dd8

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@31322 a1c6a512-1295-4272-9138-f99709370657