[FIX] qweb: variables set outside foreach must be altered by inloop t-tset

In a template, have t-set t-value outside a t-foreach
in the t-foreach, alter that variable by resetting it (as for a incrementation variable)

Before this commit, when printing the variable when the loop had finished
its value was the one set in the first place

After this commit, the value becomes the one altered by the loop iterations

closes #598

src/qweb/base_directives.ts

@@ -128,7 +128,12 @@ QWeb.addDirective({
     qwebvar.expr = `scope.${variable}`;
     if (value) {
       const formattedValue = ctx.formatExpression(value);
-      ctx.addLine(`${qwebvar.expr} = ${formattedValue};`);
+      let scopeExpr = `scope`;
+      if (ctx.protectedScopeNumber) {
+        ctx.rootContext.shouldDefineUtils = true;
+        scopeExpr = `utils.getScope(scope, '${variable}')`;
+      }
+      ctx.addLine(`${scopeExpr}.${variable} = ${formattedValue};`);
       qwebvar.value = formattedValue;
     }
 
@@ -313,7 +318,7 @@ QWeb.addDirective({
     ctx.addLine(`_${valuesID} = Object.values(_${arrayID});`);
     ctx.closeIf();
     ctx.addLine(`let _length${keysID} = _${keysID}.length;`);
-    let varsID = ctx.startProtectScope();
+    let varsID = ctx.startProtectScope(true);
     const loopVar = `i${ctx.loopNumber}`;
     ctx.addLine(`for (let ${loopVar} = 0; ${loopVar} < _length${keysID}; ${loopVar}++) {`);
     ctx.indent();