BUILD: http: stop gcc-4.1.2 from complaining about possibly uninitialized values

BUILD: http: stop gcc-4.1.2 from complaining about possibly uninitialized values

The three warnings below are totally wrong since the variables depend on another
one which is only turned on when the variables are initialized. Still this gcc-4.1.2
isn't able to see this and prefers to complain wrongly. So let's initialize the
variables to shut it up since we're not in the fast path.

src/proto_http.c: In function 'acl_fetch_any_cookie_cnt':
src/proto_http.c:8393: warning: 'val_end' may be used uninitialized in this function

src/proto_http.c: In function 'http_process_req_stat_post':
src/proto_http.c:2577: warning: 'st_next_param' may be used uninitialized in this function
src/proto_http.c:2577: warning: 'st_cur_param' may be used uninitialized in this function