remove unused variable
fix PWD in environment of sub-process (MSWin32)

this fixes the first bug in RT #65512
add a MSWin32 constant to be used for win32-specific bits
A win32 implementation based on IPC::Run
optionally require IPC::Run on Win32
implemented a check for the status of a process that works in win32 and linux
turn process_lives into a private coderef

the test script needs its own copy of the coderef,
because it is private
$SIG{CHLD} = 'IGNORE' has no effect under Win32, so we can obtain the exit status
adapt the plan for Win32
Merge branch 'win32'

Conflicts:
	lib/System/Command.pm
thanks Mithaldu
tiny documentation updates/fix
drop META files from the history
Changes for version 1.100