Windows uninstaller does not remove installation directory from PATH

[nrsiward]

The Windows installer no longer adds the installation directory multiple times to the PATH (if it is already present), but it doesn't clean up the path on uninstall. This is difficult because Inno Setup doesn't directly support PATH manipulation, since most Windows programs don't need that. The registry key that specifies the PATH can be manipulated, but removing the install folder is harder than adding it. :-)

See https://stackoverflow.com/questions/3304463/how-do-i-modify-the-path-environment-variable-when-running-an-inno-setup-install for some ideas.