crt: msvcr120 and UCRT: Fix 64 bit _(w)findfirst and _(w)findnext symbol aliases

These symbols on 64 bit should resolve to _findfirst64i32/_findnext64i32
functions, like in other CRT libraries and header files.

The UCRT 32 bit aliases are kept as they were before (even if
they are known to be incorrect); they are corrected in a separate
later commit.

Signed-off-by: Martin Storsjö <martin@martin.st>