Revert "fixed an integer overflow bug"

Author: slandelle

src/main/java/com/ning/http/client/multipart/FilePart.java

@@ -101,7 +101,7 @@ public long write(WritableByteChannel target, byte[] boundary) throws IOExceptio
 
         handler.start();
 
-        long length = 0;
+        int length = 0;
 
         length += MultipartUtils.writeBytesToChannel(target, generateFileStart(boundary));