textsplit: create isNGRAMMED() method to replace isCJK() and let the latter actually return what it says

src/rcldb/rclabstract.cpp

@@ -478,7 +478,7 @@ void Query::Native::abstractCreateSnippetsVector(
         }
         Utf8Iter uit(ent.second);
         bool newcjk = false;
-        if (TextSplit::isCJK(*uit))
+        if (TextSplit::isNGRAMMED(*uit))
             newcjk = true;
         if (!incjk || (incjk && !newcjk))
             chunk += " ";

src/rcldb/rcldb.h

@@ -202,9 +202,8 @@ public:
 
         Utf8Iter u8i(term);
         if (with_aspell) {
-            // If spelling with aspell, neither katakana nor other cjk
-            // scripts are candidates
-            if (TextSplit::isCJK(*u8i) || TextSplit::isKATAKANA(*u8i))
+            // If spelling with aspell, CJK scripts are not candidates
+            if (TextSplit::isCJK(*u8i))
                 return false;
         } else {
 #ifdef TESTING_XAPIAN_SPELL