POSIX support layer for the standard libraries.

The API of this module is unstable and not meant to be consumed by the general public. If you absolutely must depend on it, make sure to use a tight upper bound, e.g., base < 4.X rather than base < 5, because the interface can change rapidly without much warning.

This module is built on *every* platform, including Win32.

Non-POSIX compliant in order to support the following features: * S_ISSOCK (no sockets in POSIX)