Like camel_url_encode, but works directly on an existing GString.

Like camel_url_encode, but works directly on an existing GString.

	* camel-url.c (append_url_encoded): Like camel_url_encode, but
	works directly on an existing GString.
	(camel_url_to_string, output_param): Use it.
	(camel_url_encode): Likewise. Remove "escape_unsafe" arg since the
	"unsafe" chars are the ones that should *always* be escaped, and
	the places we were passing FALSE were wrong.
	(camel_url_decode): replace with a new version

	* camel-file-utils.c (camel_file_util_safe_filename): Remove extra
	arg to camel_url_encode.

	* tests/misc/url.c (main): Add tests of basic URL parsing and
	unparsing