Expose the File constructor at package level for std.process.
Update std.process to recent Phobos.
Remove obsolete TODO from std.process.
Remove some unneeded Windows prototypes from std.process.
Update usage of std.process in std.random.
Have to flush writeEnd before reading from it.
Call toArgz() and toStringz() before fork().
Cleanups and fixes wrt environ.
Use core.stdc.stdio instead of std.c.stdio.