Add arch/platform to os module

doc/api/os.markdown

@@ -10,6 +10,14 @@ Returns the hostname of the operating system.
 
 Returns the operating system name.
 
+### os.platform()
+
+Returns the operating system platform.
+
+### os.arch()
+
+Returns the operating system CPU architecture.
+
 ### os.release()
 
 Returns the operating system release.

lib/os.js

@@ -30,3 +30,9 @@ exports.cpus = binding.getCPUs;
 exports.type = binding.getOSType;
 exports.release = binding.getOSRelease;
 exports.getNetworkInterfaces = binding.getInterfaceAddresses;
+exports.arch = function() {
+  return process.arch;
+};
+exports.platform = function() {
+  return process.platform;
+};

test/simple/test-os.js

@@ -44,6 +44,14 @@ var release = os.release();
 console.log("release = ", release);
 assert.ok(release.length > 0);
 
+var platform = os.platform();
+console.log("platform = ", platform);
+assert.ok(platform.length > 0);
+
+var arch = os.arch();
+console.log("arch = ", arch);
+assert.ok(arch.length > 0);
+
 if (process.platform != 'sunos') {
   // not implemeneted yet
   assert.ok(os.loadavg().length > 0);
@@ -54,7 +62,7 @@ if (process.platform != 'sunos') {
 
 var interfaces = os.getNetworkInterfaces();
 console.error(interfaces);
-switch (process.platform) {
+switch (platform) {
   case 'linux':
     assert.equal('127.0.0.1', interfaces.lo.ip);
     break;