Add '+' sign to more keys of '-' key

Note that the tablet number/phone layout has its own '+' key.

Bug: 7255318
Change-Id: I5cc0431cf772a859eb456e9c36b07bfd0cc1278d

java/res/xml/rows_number_normal.xml

@@ -33,6 +33,8 @@
             latin:keyStyle="numKeyStyle" />
         <Key
             latin:keyLabel="-"
+            latin:moreKeys="+"
+            latin:keyLabelFlags="hasPopupHint"
             latin:keyStyle="numFunctionalKeyStyle"
             latin:keyWidth="fillRight" />
     </Row>

java/res/xml/rows_phone.xml

@@ -34,6 +34,8 @@
             latin:keyStyle="num3KeyStyle" />
         <Key
             latin:keyLabel="-"
+            latin:moreKeys="+"
+            latin:keyLabelFlags="hasPopupHint"
             latin:keyStyle="numFunctionalKeyStyle"
             latin:keyWidth="fillRight" />
     </Row>

java/res/xml/rows_phone_symbols.xml

@@ -37,6 +37,8 @@
             latin:keyStyle="numKeyStyle" />
         <Key
             latin:keyLabel="-"
+            latin:moreKeys="+"
+            latin:keyLabelFlags="hasPopupHint"
             latin:keyStyle="numFunctionalKeyStyle"
             latin:keyWidth="fillRight" />
     </Row>