Add back-slash key

This change also moves some keys,

- Infinite is moved to popup char of plus-minus.
- not-equal and nearly-equal are moved to popup chars of equal.

Bug: 3224679
Change-Id: I7c95ab5a7cd78e4dae13fb511edad607dcaed8da
diff --git a/java/res/xml-xlarge/kbd_symbols.xml b/java/res/xml-xlarge/kbd_symbols.xml
index 85deb87..a5e169d 100644
--- a/java/res/xml-xlarge/kbd_symbols.xml
+++ b/java/res/xml-xlarge/kbd_symbols.xml
@@ -139,7 +139,9 @@
         <Key
             latin:keyLabel="]" />
         <Key
-            latin:keyLabel="=" />
+            latin:keyLabel="="
+            latin:popupKeyboard="@xml/kbd_popup_template"
+            latin:popupCharacters="≠≈" />
         <Key
             latin:keyLabel=":" />
         <Key