Remove inconsistent EXTRALIBS in msvc64 config
Remove inconsistent EXTRALIBS in msvc64 config

EXTRALIBS is largely a historic artefact anyway (it applies to a very
old Platform SDK build) but EXTRALIBS is supposed to be manually
included where needed, rather than embedded in BYTECCLIBS and
NATIVECCLIBS.

gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml