Document the limitations of Linkify addresses

Explain that we are using WebView#findAddresses() which is
limited to US addresses at the moment (at least according
to its documentation), among various other limitations.

Bug: 5847264
Change-Id: If86c6d7c11cc080f0fe3401ffb7bce8068c6016f

core/java/android/text/util/Linkify.java

@@ -78,7 +78,10 @@ public class Linkify {
 
     /**
      *  Bit field indicating that street addresses should be matched in methods that
-     *  take an options mask
+     *  take an options mask. Note that this uses the
+     *  {@link android.webkit.WebView#findAddress(String) findAddress()} method in
+     *  {@link android.webkit.WebView} for finding addresses, which has various
+     *  limitations.
      */
     public static final int MAP_ADDRESSES = 0x08;