64-bit Installer can detect the 32-bit installation (and vice versa),
and suggest users to remove the existing one before install the new one.
It works only when the existing installation is on "C:\Program Files
(x86)\Notepad++" or "C:\Program Files\Notepad++" directory
After uninstalling 64-bit Notepad++ via uninstaller, the entry remains in
the "uninstall programs" section of panel of configuration. This commit fixes the bug.
Don Ho