new lint: using collect() to just exhaust an iterator

Should use a for loop instead.

src/lib.rs

@@ -96,6 +96,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
         loops::EXPLICIT_ITER_LOOP,
         loops::ITER_NEXT_LOOP,
         loops::NEEDLESS_RANGE_LOOP,
+        loops::UNUSED_COLLECT,
         loops::WHILE_LET_LOOP,
         matches::MATCH_REF_PATS,
         matches::SINGLE_MATCH,