Raise an error when attempting to close stdio or stderr

[d-torrance]

stdio supports both input and output, so we check in both closeIn and closeOut

stderr only supports output, so we only check in closeOut (stderr << closeIn already raises an error since it's not open for input)

Closes: #4392

No AI used!

Before

i1 : stdio << close
stdio:1:6:(3):[1]: error: at print: expected an output file
stdio:1:6:(3):[1]: error: after print: expected an output file

i1 : stderr << close

o1 = stderr

o1 : File

i2 : 1/0

i3 : -- where's the error message?

After

i1 : stdio << close
stdio:1:6:(3):[1]: error: can't close stdio

i2 : stderr << close
stdio:2:7:(3):[1]: error: can't close stderr

[MichaelABurr]

Simple, and looks OK to me. I don't expect this code to be encountered frequently, so I don't expect a performance hit.