Add "emergency calling" warning when WFC doesn't support emergency calls.

Some carriers cannot place emergency calls over WFC.  Adding a warning
message above the dial pad when the device is on WFC and emergency calls
are not available.

Test: Manual
Bug: 68030294
Change-Id: Icce8ca2427371232d336b63c3985226551949973
diff --git a/res/values/strings.xml b/res/values/strings.xml
index 540876e..8234af3 100644
--- a/res/values/strings.xml
+++ b/res/values/strings.xml
@@ -1133,6 +1133,9 @@
     <string name="dial_emergency_error">Can\'t call. <xliff:g id="non_emergency_number">%s</xliff:g> is not an emergency number.</string>
     <!-- Emergency dialer: message displayed in an error dialog -->
     <string name="dial_emergency_empty_error">Can\'t call. Dial an emergency number.</string>
+    <!-- Message displayed over top of the emergency dialer dialpad indicating to the user that
+         emergency calling is not currently available. -->
+    <string name="dial_emergency_calling_not_available">Emergency calling not available</string>
 
     <!-- Displayed in the text entry box in the dialer when in landscape mode to guide the user
          to dial using the physical keyboard -->