Original commit message from CVS:
* gst/gstbin.c: (gst_bin_child_proxy_get_child_by_index),
(gst_bin_child_proxy_get_children_count):
* gst/gstchildproxy.c: (gst_child_proxy_get_child_by_name),
(gst_child_proxy_lookup), (gst_child_proxy_get_property),
(gst_child_proxy_get_valist), (gst_child_proxy_set_property),
(gst_child_proxy_set_valist):
* gst/parse/grammar.y:
Make ChildProxy threadsafe and fix mem leaks.