Fix this; previously it would discard the entire message body after

Fix this; previously it would discard the entire message body after

	* libsoup/soup-message-body.c (soup_message_body_wrote_chunk): Fix
	this; previously it would discard the entire message body after
	writing a SOUP_MEMORY_TEMPORARY chunk. Part of WebKit bug 18343.

	* libsoup/soup-message-io.c (io_write): use
	io->write_chunk->length *before* freeing io->write_chunk.

	* tests/chunk-test.c (do_temporary_test): new test to make sure
	that TEMPORARY buffers are handled properly.

svn path=/trunk/; revision=1232