Implement URI encoding quirk for iTunes and Roku

iTunes and Roku devices do not encode + as %2B in the query string and
do not encode space as + either in the query string (though at least the
Roku encode space as %20 everywhere). This needs to be worked around or
browse queries fail to parse because + was decoded as space when the query
really needs a + character.

src/httpd.h

@@ -9,6 +9,9 @@
 void
 httpd_stream_file(struct evhttp_request *req, int id);
 
+char *
+httpd_fixup_uri(struct evhttp_request *req);
+
 int
 httpd_basic_auth(struct evhttp_request *req, char *user, char *passwd, char *realm);