Intern SYSTEM:AVAILABLE-ENCODINGS symbols

(robert Dodier)

c.f. <armedbear/abcl#82>

git-svn-id: https://abcl.org/svn/trunk/abcl@15114 1c010e3e-69d0-11dd-93a8-456734b0d56f

src/org/armedbear/lisp/Stream.java

@@ -396,7 +396,7 @@ static public List<Symbol> availableEncodings() {
     SortedMap<String, Charset> available = Charset.availableCharsets();
     Set<String> encodings = available.keySet();
     for (String charset : encodings) {
-      result.add(new Symbol(charset, PACKAGE_KEYWORD));
+      result.add (PACKAGE_KEYWORD.intern (charset));
     }
     return result;
   }