WIP WinCE
Configure: Make -Dsysroot work with gcc$_exe
Configure, sysroot: Always set usrinc and friends.

The except now is that, if -Dsysroot was set, failing
to find any of them is not an exception.
Configure: Support for cross-compiling to Win32
Configure: When cross-compiling, save the $^O of the host
Configure: Minor improvements to the building on the host miniperl
Makefile.SH: Changes to allow cross-compiling to Win32
WIP Linux -> Win32 cross compilation