[FIX] compiler: allow t-model.number to work with select

Before this commit, owl parser would ignore the `.number` suffix on
<select> options. I do not see a good reason for that, and it prevents
some legitimate usecases.

closes #1444

tests/compiler/parser.test.ts

@@ -1991,8 +1991,8 @@ describe("qweb parser", () => {
       baseExpr: "state",
       expr: "'stuff'",
       eventType: "click",
-      shouldNumberize: false,
-      shouldTrim: false,
+      shouldNumberize: true,
+      shouldTrim: true,
       targetAttr: "value",
       hasDynamicChildren: false,
       specialInitTargetAttr: "checked",