Edata: zero stack edatas before initializing.

This avoids some UB. No compilers take advantage of it for now, but no sense in
tempting fate.

src/emap.c

@@ -247,7 +247,7 @@ emap_split_prepare(tsdn_t *tsdn, emap_t *emap, emap_prepare_t *prepare,
 	 * and commit state, and head status.  This is a fake edata_t, used to
 	 * facilitate a lookup.
 	 */
-	edata_t lead;
+	edata_t lead = {0};
 	edata_init(&lead, 0U, edata_addr_get(edata), size_a, false, 0, 0,
 	    extent_state_active, false, false, false, EXTENT_NOT_HEAD);
 

src/extent_dss.c

@@ -198,7 +198,7 @@ extent_alloc_dss(tsdn_t *tsdn, arena_t *arena, void *new_addr, size_t size,
 					*commit = pages_decommit(ret, size);
 				}
 				if (*zero && *commit) {
-					edata_t edata;
+					edata_t edata = {0};
 					ehooks_t *ehooks = arena_get_ehooks(
 					    arena);