depends: Add libevent compatibility patch for windows

Add a patch that seems to be necessary for compatibilty of libevent
2.0.22 with recent mingw-w64 gcc versions (at least GCC 5.3.1 from Ubuntu
16.04).

Without this patch the Content-Length in the HTTP header ends up as
Content-Length: zu, causing communication between the RPC
client and server to break down. See discussion in #8653.

Source: https://sourceforge.net/p/levent/bugs/363/

Thanks to @sstone for the suggestion.