strip leading slashes from name in ZipFile.getEntry

This is necessary to allow resource loading of the form
Foo.class.getResourceAsStream("/foo.txt") from JAR files.

classpath/java/util/zip/ZipFile.java

@@ -74,6 +74,9 @@ public class ZipFile {
   }
 
   protected ZipEntry getEntry(EntryFactory factory, String name) {
+    while (name.startsWith("/")) {
+      name = name.substring(1);
+    }
     Integer pointer = index.get(name);
     return (pointer == null ? null : factory.makeEntry(window, pointer));
   }