Merged revisions r1565300-r1565416 from tomcat/trunk:
Improve handling of file upload errors. Display a message instead of error 500 page.
Simplify parts handling code, as it is known that Tomcat takes care of them when recycling a request.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/tc7.0.x/trunk@1565419 13f79535-47bb-0310-9956-ffa450edef68