docs/plugins/: Add souphttpsrc to the docs.

docs/plugins/: Add souphttpsrc to the docs.

Original commit message from CVS:
Patch by: Wouter Cloetens <wouter at mind dot be>
* docs/plugins/Makefile.am:
* docs/plugins/gst-plugins-bad-plugins-docs.sgml:
* docs/plugins/gst-plugins-bad-plugins-sections.txt:
Add souphttpsrc to the docs.
* configure.ac:
* ext/soup/gstsouphttpsrc.c: (gst_souphttp_src_class_init),
(gst_souphttp_src_init), (gst_souphttp_src_dispose),
(gst_souphttp_src_set_property), (gst_souphttp_src_get_property),
(gst_souphttp_src_cancel_message),
(gst_souphttp_src_queue_message),
(gst_souphttp_src_add_range_header),
(gst_souphttp_src_session_unpause_message),
(gst_souphttp_src_session_pause_message),
(gst_souphttp_src_session_close),
(gst_souphttp_src_got_headers_cb), (gst_souphttp_src_got_body_cb),
(gst_souphttp_src_finished_cb), (gst_souphttp_src_got_chunk_cb),
(gst_souphttp_src_response_cb), (gst_souphttp_src_parse_status),
(gst_souphttp_src_create), (gst_souphttp_src_start),
(gst_souphttp_src_stop), (gst_souphttp_src_unlock),
(gst_souphttp_src_unlock_stop), (gst_souphttp_src_get_size),
(gst_souphttp_src_is_seekable), (gst_souphttp_src_do_seek),
(gst_souphttp_src_set_location), (gst_souphttp_src_set_proxy),
(plugin_init):
* ext/soup/gstsouphttpsrc.h:
Add support for libsoup2.4 and require it. Also implement redirection
and manual proxy specification. Fixes bug #510708.
* tests/check/Makefile.am:
* tests/check/elements/.cvsignore:
* tests/check/elements/souphttpsrc.c:
Add unit test for souphttpsrc.