I/O: Standard output/error hung on MINGW64

[yannoff]

Happens sometimes randomly and unexpectedly on MINGW64.

Not only the console outputs don't work, but standard output/error streams are blocked and then unsubable by other shell applications.

Despite the official PHP recommendations, seems it's safer to open streams manually instead of using the apposite STDIN / STDERR / STDOUT constants, at least we can close previously opened handles manually at destruct time.