`src/3rd_party/faiss/utils/misc.h` doesn't compile on Cygwin, include `<cstdint>`

[polkovnikov]

Bug description

As a part of another project marian doesn't compile in Windows Cygwin's GCC when file src/3rd_party/faiss/utils/misc.h is included.

This file needs #include <cstdint>, because int64_t is used inside of it.

Probably Linux version of GCC by default includes this <cstdint> hence you didn't notice.