Make std.file.getTimes safe

On Windows systems, it does not contain any unsafe operations.
On Posix systems, it contains the following unsafe operations but we can verify that they can be trusted.
- use of an unsafe function `core.sys.posix.sys.stat.stat`
- taking an address of a local variable (`statbuf`)

can't you simplify this by making `trustedStat` take `statbuf` as reference argument and taking address inside the function (`ptrOfLocalVariable` can be removed then)