We use pkg-config where we can, which generally replaces libtool at a
higher level and does not have the same downsides as libtool. These
archives sit in our depends tree with no purpose and pollute the final
bitcoin build with massive overlinking.
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.
