os: name every anonymous function in OS module

There are too many anonymous functions in the source code which makes
the debugging frustrating.

We are fixing this issue by naming every anonymous function in all the
modules.As part of which,this commit contains changes to os module

lib/os.js

@@ -23,15 +23,15 @@ Object.defineProperty(exports, 'constants', {
   value: constants
 });
 
-exports.arch = function() {
+exports.arch = function arch() {
   return process.arch;
 };
 
-exports.platform = function() {
+exports.platform = function platform() {
   return process.platform;
 };
 
-exports.tmpdir = function() {
+exports.tmpdir = function tmpdir() {
   var path;
   if (isWindows) {
     path = process.env.TEMP ||
@@ -62,6 +62,6 @@ exports.getNetworkInterfaces = internalUtil.deprecate(function() {
 exports.EOL = isWindows ? '\r\n' : '\n';
 
 if (binding.isBigEndian)
-  exports.endianness = function() { return 'BE'; };
+  exports.endianness = function endianness() { return 'BE'; };
 else
-  exports.endianness = function() { return 'LE'; };
+  exports.endianness = function endianness() { return 'LE'; };