Add software features for SIP and VOIP

and block SipService creation and SIP API if the feature is not available.

Change-Id: Icf780af1ac20dda4d8180cea3e5b20e21a8350bc
diff --git a/services/java/com/android/server/SystemServer.java b/services/java/com/android/server/SystemServer.java
index 1a209e2..4a286e7 100644
--- a/services/java/com/android/server/SystemServer.java
+++ b/services/java/com/android/server/SystemServer.java
@@ -418,10 +418,13 @@
             }
 
             try {
-                Slog.i(TAG, "Sip Service");
-                ServiceManager.addService("sip", new SipService(context));
+                SipService sipService = SipService.create(context);
+                if (sipService != null) {
+                    Slog.i(TAG, "Sip Service");
+                    ServiceManager.addService("sip", sipService);
+                }
             } catch (Throwable e) {
-                Slog.e(TAG, "Failure starting DiskStats Service", e);
+                Slog.e(TAG, "Failure starting SIP Service", e);
             }
         }