win32: fix win32 installers generation
cd0c51c07e5f introduced a typo preventing a proper generation of the
installers. Also remove ConcatenateFiles() function as it is no more
required.
Welcome to Mercurial for Windows!
---------------------------------
For configuration and usage directions, please read the ReadMe.html
file that comes with this package.
Also check the release notes at:
http://mercurial.selenic.com/wiki/WhatsNew