save some memory by reordering fields in various structs

Saving memory is a new year resolution for some, see [1] and [2].
With the help of pahole (from dwarves, linux only) we can put some
structs to diet. We are starting from legion related structs (uwsgi_legion,
uwsgi_legion_node) and wsgi_request.
There are more struct that have holes that can be avoided by just
reordering fields.
I'm wondering if a smaller wsgi_request make a measurable difference
in performance, benchmarking is appreciated.
Please review.

[1] http://www.catb.org/esr/structure-packing/
[2] http://blog.libtorrent.org/2013/12/memory-cache-optimizations/