build: fix mingw miniupnpc cflags
Summary:
Pulls in a patch I've upstreamed to miniupnpc so that we properly pass our cflags when building it for mingw. See miniupnp/miniupnp#619. Also set D_WIN32_WINNT to 0x0601 to match libevent, configure etc. Previously it was being set to 0X501.
Backport of core#25964.
Depends on D16562.
Test Plan: Run the GUIX builds.
Reviewers: #bitcoin_abc, PiRK
Reviewed By: #bitcoin_abc, PiRK
Differential Revision: https://reviews.bitcoinabc.org/D16563