Rename VoLTE/WFC enable API to available - add VT available API. [DO NOT MERGE]

Renamed API to use consistent semantics: available refers to the current
state of the service rather then whether feature is enabled by device/carrier/
user.

Added VT API to match VoLTE/WFC.

Change-Id: Ifb31f123db77e731e75a982b8594168f59a289e7

telephony/java/android/telephony/TelephonyManager.java

@@ -3786,13 +3786,13 @@ public class TelephonyManager {
        }
    }
 
-   /**
-    * Returns the Status of Volte
-    *@hide
-    */
-   public boolean isVolteEnabled() {
+    /**
+     * Returns the Status of Volte
+     * @hide
+     */
+    public boolean isVolteAvailable() {
        try {
-           return getITelephony().isVolteEnabled();
+           return getITelephony().isVolteAvailable();
        } catch (RemoteException ex) {
            return false;
        } catch (NullPointerException ex) {
@@ -3800,13 +3800,27 @@ public class TelephonyManager {
        }
    }
 
-   /**
-    * Returns the Status of Wi-Fi Calling
-    *@hide
-    */
-   public boolean isWifiCallingEnabled() {
+    /**
+     * Returns the Status of video telephony (VT)
+     * @hide
+     */
+    public boolean isVideoTelephonyAvailable() {
+        try {
+            return getITelephony().isVideoTelephonyAvailable();
+        } catch (RemoteException ex) {
+            return false;
+        } catch (NullPointerException ex) {
+            return false;
+        }
+    }
+
+    /**
+     * Returns the Status of Wi-Fi Calling
+     * @hide
+     */
+    public boolean isWifiCallingAvailable() {
        try {
-           return getITelephony().isWifiCallingEnabled();
+           return getITelephony().isWifiCallingAvailable();
        } catch (RemoteException ex) {
            return false;
        } catch (NullPointerException ex) {

telephony/java/com/android/internal/telephony/ITelephony.aidl

@@ -876,13 +876,19 @@ interface ITelephony {
      * Returns the Status of Wi-Fi Calling
      *@hide
      */
-    boolean isWifiCallingEnabled();
-
-     /**
+    boolean isWifiCallingAvailable();
+    
+    /**
      * Returns the Status of Volte
      *@hide
      */
-    boolean isVolteEnabled();
+    boolean isVolteAvailable();
+
+     /**
+     * Returns the Status of VT (video telephony)
+     *@hide
+     */
+    boolean isVideoTelephonyAvailable();
 
     /**
       * Returns the unique device ID of phone, for example, the IMEI for