8029800: Flags.java uses String.toLowerCase without specifying Locale

Introducing StringUtils.toLowerCase/toUpperCase independent on the default locale, converting almost all usages of String.toLowerCase/toUpperCase to use the new methods.

Reviewed-by: jjg, bpatel

langtools/test/tools/javac/util/StringUtilsTest.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/**
+ * @test
+ * @bug 8029800
+ * @summary Unit test StringUtils
+ * @run main StringUtilsTest
+ */
+
+import java.util.Locale;
+import java.util.Objects;
+import com.sun.tools.javac.util.StringUtils;
+
+public class StringUtilsTest {
+    public static void main(String... args) throws Exception {
+        new StringUtilsTest().run();
+    }
+
+    void run() throws Exception {
+        Locale.setDefault(new Locale("tr", "TR"));
+
+        //verify the properties of the default locale:
+        assertEquals("\u0131", "I".toLowerCase());
+        assertEquals("\u0130", "i".toUpperCase());
+
+        //verify the StringUtils does what it should
+        assertEquals("i", StringUtils.toLowerCase("I"));
+        assertEquals("I", StringUtils.toUpperCase("i"));
+
+        //verify we can use index from indexOf of toLowerCase String in the original:
+        assertEquals(2, StringUtils.toLowerCase("\u0130\u0130lookFor").indexOf("lookfor"));
+    }
+
+    void assertEquals(String expected, String actual) {
+        if (!Objects.equals(expected, actual)) {
+            throw new IllegalStateException("expected=" + expected + "; actual=" + actual);
+        }
+    }
+
+    void assertEquals(int expected, int actual) {
+        if (expected != actual) {
+            throw new IllegalStateException("expected=" + expected + "; actual=" + actual);
+        }
+    }
+}