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Conflicts:
	docs/plugins/gstreamer-plugins.hierarchy
	gst/gstelement.c

_trim -> _resize
_create_sub -> copy_region

Also add a test for naming pads by the caller and return NULL
when requesting an already existing pad.

Allow for automatic merging of memory block in the _map function and automatic
freeing of the temporary memory.
Remove some unneeded functions.
Add possibility to force writable spanned memory.

Especially check if a pad with that name already exists.

Use the string provided by the caller for the sinkpad name
if possible. Note that all sanity checking for this name
is already done in GstElement.

Fixes Bug #645931

Conflicts:
	gst/gst.c
	libs/gst/base/gstcollectpads.c

Automatically make the memory of a buffer writable when the buffer is writable
and the memory is asked to mapped WRITE.
Add docs