Make it possible to configure a GDestroyNotify and user_data for
gst_memory_new_wrapped() this allows for more flexible wrapping of foreign
memory blocks.

Use a structure to hold info about the mapping. The application then keeps track
of this state and we can use it to unmap the memory again later.

When _clear gets called between _map and _unmap, buffers
will be unreffed. If the adapter was mapped, memory leaks
may occur.
While calling _clear between _map and _unmap does not seem
like such a great idea, this is possible in the audio
encoder base class, as _clear may be called in _finish_frame.
Since the audio encoder relies on flushing to keep track of
timestamps, delaying flushing till after handle_frame seems
dangerous.
So, we unmap on clear, as the next unmap will do nothing.
This makes _clear safe to call between _map and _unmap,
while avoiding leaking the mapped buffer.

https://bugzilla.gnome.org/show_bug.cgi?id=664133

Fixes compiler warnings on OSX:
gstadapter.h:82: warning: type qualifiers ignored on function return type
gstadapter.c:412: warning: type qualifiers ignored on function return type

const gpointer is not the same as gconstpointer or const void *.

https://bugzilla.gnome.org/show_bug.cgi?id=664491

Use a stack-allocated GQueue to assemble our GList.

Fixes build on MacOSX
Signed-off-by: Edward Hervey <edward.hervey@collabora.co.uk>

Add an index to gst_buffer_take_memory() so that we can also insert memory at a
certain offset. This is mostly interesting to prepend a header memory block to
the buffer.

Also remove GST_PAD_CHECKGETRANGEFUNC macro

_trim -> _resize
_create_sub -> copy_region

Many of these are superfluous and were added for clarity.

Add some gtk-doc Since: markers, fix one Since: marker,
fix typo.

Add a function to retrieve a list of buffers containing the first N bytes from
the adapter. This can be done without a memcpy and should make it possible to
transfer the list to a GstBufferList later.

Optimize _peek() some more by reusing already assembled data when we can.

When we have already assembled some data before, reuse this data and only copy
the part that is new.

Move some common code into one place

Add support for 0 sized buffers. This is interesting in combination with the
timestamp functions.

Fixes #629553

Retain the last scanned buffer entry and offset, so we can resume buffer
scanning there in case of a typical progressive scan.
Also potentially optimize _copy subsequently occurring in that area.

Also add to .def and docs.

Fixes #619828.

API: gst_adapter_masked_scan_uint32_peek

That is, provide correct return value (as documented), and actually
loop to consider more than the first 2 buffers.

Trims off 10-20% cpu time when using gst_adapter_take[_buffer]

This avoids:
* triple-checking for the GType when type-checking is enabled (see #597260)
* Avoids going through an expensive no-argument checking which landed in
  glib-2.22
* Avoids going through 2 extrac functions (g_object_new -> g_object_new_valist)

Clarify byte reader docs a bit: offset is relative to the current
position of the reader, not to the start of the data. Also, the
examples in both the adapter docs and the byte reader docs have
the mask and pattern arguments swapped (see #587561). Spotted
by Carl-Anton Ingmarsson.

This category can be used to log slow code path and help auditing the
performance. Add FIXME-0.11 to some questionable categories.

gst_adapter_masked_scan_uint32 could return values smaller than offset
if the first byte(s) of the mask are 0 and the pattern matches the
beginning of the adapter.
Added examples to documentation of gst_adapter_masked_scan_uint32().
Also added some more masked boundary tests.
Fixes #584118

Remove a compare and branch from flush.