[perl #132258] [SECURITY][WIN32] `run "perl6" ...` can be made to execute shell commands

[Zoffix Znet via RT]

Worse still; there doesn't seem to be a way to make `run` work with `cmd.exe` 
commands at all. Even if you escape the args yourself properly, they seem to 
get butchered by libuv's quoting. There's a 
UV_PROCESS_WINDOWS_VERBATIM_ARGUMENTS that'd avoid quoting, though currently we 
have it off (so non-cmd.exe args get processed right)