cmdutil: hide child window created by win32 spawndetached()
Hiding the child process window is not strictly necessary but it avoids opening
an empty shell window when running hg serve as well as a task in the task bar.
The window is hidden after the process is already started causing a single
flicker.
Find right hg command for detached process
On Windows, Mercurial can be run from the python script of from a frozen
executable. In the first case, we have to call the python interpreter since the
script is not executable. Frozen executable can be called directly.
Fix 3/3 for
issue421