Mingw ::unlink problem.

[Bo Peng]

Dear list,

It has been a while since I compile lyx 1.5.x with mingw. I get the
following error message:

src\support\unlink.C:26: error: '::unlink has not been declared.

I can see that mingw has unistd.h and HAVE_UNISTD_H is defined.

Bo