Code cleanup, make it adhere to the Gnome/Gtk+ code formatting, which is quite clean and more readable.

Original commit message from CVS:
Code cleanup, make it adhere to the Gnome/Gtk+ code formatting, which is
quite clean and more readable.
Renamed parseavi to avidecoder
Implemented seeking/time display/pause/play/stop/clean exit to gstmediaplay
Added an element flag to indicate that it cannot deal with noncontigous
buffers. If such an element is found in the pipeline, seeking is disabled
for the complete stream (avidecoder cannot deal with seeking until we convert
it to a loop based element with pull_region to fetch the indeces etc...)