nmake script LIBS variable uses .a instead of .lib
In src/or/Makefile.nmake the LIBS variable refernces third-party libraries libevent.a, libcrypto.a, libssl.a and libz.a. This file extension confuses the MSVC linker, which will print warnings about unknown type and "assuming". Using the .lib file extension is more appropriate since this is what the linked projects use. Curiously enough, src/test/Makefile.nmake already has this 'fix', so I'm not sure what happened there.
PS: there's a naming inconsistency: libcrypto -> libeay32, libssl -> ssleay32, libz -> zlib these are easily worked around using symlinks, but it makes me wonder if openssl has a toggle for the legacy/defunct eay product imitation.