Define phone_accounts to fix build breaks.

I'm not sure what happened, but this string is defined in many of the
string.xmls, but not the base one... there are breaks in branches
which lmp-dev merges into because phone_accounts isn't defined. Thus,
adding this definition to fix those breaks.

Bug: 544757
Change-Id: I8457db022eec9402e48dd254b4a2b6c77406ed9d
diff --git a/res/values/strings.xml b/res/values/strings.xml
index 02eb9c8..34cd0f1 100644
--- a/res/values/strings.xml
+++ b/res/values/strings.xml
@@ -125,6 +125,8 @@
     <!-- Label for the "Network settings" screen in the Settings UI -->
     <string name="settings_label">Network settings</string>
 
+    <!-- Label for settings screen for phone accounts. -->
+    <string name="phone_accounts">Phone account settings</string>
     <!-- Label for list item which opens a dialog to select the default outgoing account -->
     <string name="phone_accounts_make_calls_with">Make calls with</string>
     <!-- Label for list item which opens a dialog to select the default outgoing account for SIP calls. -->