many fixes related to dynamic pipelines.

many fixes related to dynamic pipelines.

Original commit message from CVS:
* many fixes related to dynamic pipelines.
* addition of gst_element_disconnect_elements(), as per connect_elements()
* don't have a cow if typefind changes state in its signal handlers
* support of request pad -> request pad in connect_elements()
* some fixes in int2float that will eventually need to be ported to float2int and
adder

the gstelement api is getting bloated, expect a rewrite within the next month.