After your hints now I have ~90KB for 32 bits and ~86KB for 64 bits.
$ make clean
$ CFLAGS='-Os -s' ./configure --disable-doc --disable-examples --disable-messages --enable-https=no --disable-bauth --disable-dauth --disable-curl
$ make install-strip
And got the compiled file on `C:\msys32\usr\local\bin\libmicrohttpd-12.dll`.
I don't know why MHD calls the `libwinpthread-1.dll` lib even without use the `MHD_USE_THREAD_PER_CONNECTION` flag, but it isn't problem, I can distribute the two library.
I believe the is time to send the updated Windows binaries to the MHD home page.
Thanks a lot Evg! :-)
(I'm indicating MHD in many lists that I participate :-) )