Fix: require.async module exception delegation

The fs.readFile bug was hiding another bug that was causing this test
to pass, even so it was broken:

require.async("../fixtures/throws_error1") in test-module-loading.js

This patch fixes the original test by running _compile within a
try..catch block for _loadScript.

_loadScriptSync also had some useless (deprecated?) code for dealing
with module entry point exceptions. This code was also removed for
greater clarity.

lib/module.js

@@ -390,12 +390,8 @@ Module.prototype._compile = function (content, filename) {
 
 Module.prototype._loadScriptSync = function (filename) {
   var content = requireNative('fs').readFileSync(filename, 'utf8');
-  var e = this._compile(content, filename);
-  if (e) {
-    throw e;
-  } else {
-    this.loaded = true;
-  }
+  this._compile(content, filename);
+  this.loaded = true;
 };
 
 
@@ -406,16 +402,18 @@ Module.prototype._loadScript = function (filename, callback) {
     if (err) {
       if (callback) callback(err);
     } else {
-      var e = self._compile(content, filename);
-      if (e) {
-        if (callback) callback(e);
-      } else {
-        self._waitChildrenLoad(function () {
-          self.loaded = true;
-          if (self.onload) self.onload();
-          if (callback) callback(null, self.exports);
-        });
+      try {
+        self._compile(content, filename);
+      } catch (err) {
+        if (callback) callback(err);
+        return;
       }
+
+      self._waitChildrenLoad(function () {
+        self.loaded = true;
+        if (self.onload) self.onload();
+        if (callback) callback(null, self.exports);
+      });
     }
   });
 };