gst/: Make gst_caps_replace() work like other _replace() functions.

gst/: Make gst_caps_replace() work like other _replace() functions.

Original commit message from CVS:
* gst/base/gstbasesink.c: (gst_basesink_base_init),
(gst_basesink_pad_getcaps), (gst_basesink_init),
(gst_basesink_chain_unlocked):
* gst/base/gsttypefindhelper.c: (helper_find_suggest),
(gst_type_find_helper):
* gst/elements/gsttypefindelement.c:
(gst_type_find_element_have_type), (gst_type_find_element_init),
(stop_typefinding), (gst_type_find_element_handle_event),
(find_suggest), (gst_type_find_element_chain),
(gst_type_find_element_checkgetrange),
(gst_type_find_element_getrange), (do_typefind),
(gst_type_find_element_activate):
* gst/gstbuffer.c: (_gst_buffer_sub_free),
(gst_buffer_default_free), (gst_buffer_default_copy),
(gst_buffer_set_caps):
* gst/gstcaps.c: (gst_caps_ref), (gst_caps_unref),
(gst_caps_replace):
* gst/gstmessage.c: (gst_message_new),
(gst_message_new_state_changed):
* gst/gstpad.c: (gst_pad_set_active), (gst_pad_peer_set_active),
(gst_pad_set_checkgetrange_function),
(gst_pad_link_prepare_filtered), (gst_pad_relink_filtered),
(gst_pad_set_caps), (gst_pad_check_pull_range),
(gst_pad_pull_range), (gst_static_pad_template_get_caps):
* gst/gstpad.h:
* gst/gsttypefind.c: (gst_type_find_register):
Make gst_caps_replace() work like other _replace() functions.
Use _caps_replace() where possible.
Make sure _message_new() initialises its field.
Add gst_static_pad_template_get_caps()