Detecting VT support
====================
Three possible outcomes:
- VT emu supported
- VT emu not supported
- error occurred during testing
For testing whether it's supported:
- try to set ENABLE_VIRTUAL_TERMINAL_PROCESSING
- if no error returned -> VT emu is supported
- if an error is returned, cast it to a syscall.Errno
- if it is not a syscall.Errno -> error occurred during testing
- if it is one and it's value != 87 -> error occurred during testing
- if it is one and it's value == 87 -> V emu not supported