IO-171 Document that IOCase assumes there are only two OSes: Windows and Unix

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/io/trunk@1002159 13f79535-47bb-0310-9956-ffa450edef68

Author: Niall Pemberton

src/java/org/apache/commons/io/IOCase.java

@@ -51,6 +51,11 @@ public final class IOCase implements Serializable {
      * The constant for case sensitivity determined by the current operating system.
      * Windows is case-insensitive when comparing filenames, Unix is case-sensitive.
      * <p>
+     * <strong>Note:</strong> This only caters for Windows and Unix. Other operating
+     * systems (e.g. OSX and OpenVMS) are treated as case sensitive if they use the
+     * Unix file separator and case-insensitive if they use the Windows file separator
+     * (see {@link java.io.File#separatorChar}).
+     * <p>
      * If you derialize this constant of Windows, and deserialize on Unix, or vice
      * versa, then the value of the case-sensitivity flag will change.
      */