docs/design/part-synchronisation.txt: Update some docs.

Original commit message from CVS:
* docs/design/part-synchronisation.txt:
Update some docs.
* docs/plugins/Makefile.am:
* docs/plugins/gstreamer-plugins-docs.sgml:
* docs/plugins/gstreamer-plugins-sections.txt:
* plugins/elements/gstmultiqueue.c:
Add multiqueue to the docs.
6 files changed