upload module 2.1.1

[Valery Kholodkov]

Greetings!

I have to move forward somehow and I open a new branch 2.1 of upload
module as well as experiment #1. Will see whether on-the-fly processing of
files makes sense.

Changes to this branch basically are:

 * Added feature: upload filters, unzip and discarding filter
 * Added feature: guessing content type using file extensions
 * Added feature: specifying list of void content types via
 upload_void_content_type directive

I'll continue to maintain two branches, but if it this turns out to be a
useful feature, I'll merge everything to branch 2.1.

NOTE 1: for ZIP files with many entries it is necessary to increase value
of upload_max_output_body_len parameter.

NOTE 2: Packagers are not recommended to switch to this branch.

Please see details on this page:
http://www.grid.net.ru/nginx/upload.en.2.1.1.html

-- 
Best regards,
Valery Kholodkov