(#11847) Don't hard code ruby install paths in Windows batch files

Previously, the {filebucket,pi,puppet,puppetdoc,ralsh}.bat files hard
coded the path to the ruby installation, making it impossible to move
the ruby install directory.

This commit changes the script to use the %~dp0 batch file modifier,
which resolves to the drive letter and path of the directory of the
batch file being executed.

Windows XP and later all support the %* modifier, so this commit
removes the Win 9x code paths that are not supported.