MINOR: http: export http_get_path() function

This patch simply exports the http_get_path() function from the proto_http.c file.
diff --git a/include/proto/proto_http.h b/include/proto/proto_http.h
index 8385dc6..dfa094a 100644
--- a/include/proto/proto_http.h
+++ b/include/proto/proto_http.h
@@ -112,6 +112,7 @@
 unsigned int http_get_hdr(const struct http_msg *msg, const char *hname, int hlen,
 			  struct hdr_idx *idx, int occ,
 			  struct hdr_ctx *ctx, char **vptr, int *vlen);
+char *http_get_path(struct http_txn *txn);
 
 struct http_txn *http_alloc_txn(struct stream *s);
 void http_init_txn(struct stream *s);