Code style: Fix ESLint "no-prototype-builtins" errors

Part of #407.

lib/compiler/index.js

@@ -8,7 +8,7 @@ function processOptions(options, defaults) {
   });
 
   Object.keys(defaults).forEach(name => {
-    if (!processedOptions.hasOwnProperty(name)) {
+    if (!Object.prototype.hasOwnProperty.call(processedOptions, name)) {
       processedOptions[name] = defaults[name];
     }
   });

lib/compiler/passes/report-duplicate-labels.js

@@ -33,7 +33,7 @@ function reportDuplicateLabels(ast) {
     action: checkExpressionWithClonedEnv,
 
     labeled(node, env) {
-      if (env.hasOwnProperty(node.label)) {
+      if (Object.prototype.hasOwnProperty.call(env, node.label)) {
         throw new GrammarError(
           "Label \"" + node.label + "\" is already defined "
             + "at line " + env[node.label].start.line + ", "

lib/compiler/passes/report-duplicate-rules.js

@@ -9,7 +9,7 @@ function reportDuplicateRules(ast) {
 
   let check = visitor.build({
     rule(node) {
-      if (rules.hasOwnProperty(node.name)) {
+      if (Object.prototype.hasOwnProperty.call(rules, node.name)) {
         throw new GrammarError(
           "Rule \"" + node.name + "\" is already defined "
             + "at line " + rules[node.name].start.line + ", "

lib/compiler/visitor.js

@@ -61,7 +61,7 @@ let visitor = {
     };
 
     Object.keys(DEFAULT_FUNCTIONS).forEach(type => {
-      if (!functions.hasOwnProperty(type)) {
+      if (!Object.prototype.hasOwnProperty.call(functions, type)) {
         functions[type] = DEFAULT_FUNCTIONS[type];
       }
     });