safer behavior:

  - the (un)installer refuses to do anything if it finds a currently running Pd(64).

  - check if there's write permission on target dir before attempting to do anything else.

troubleshoot tools:

  - tool to clear Pd(64) preferences. (only runs at user scope).

  - tool to set which Pd(64) installation is used to open .pd files (scope can be user or allusers).

  - also these two tools are included in the uninstaller but here the '.pd' files repair is automatic (you don't have to choose which app).

user scope:

  - admin users can choose to install or run troubleshot tools at user or allusers scope.

alternate install:

  - user can choose to do an alternate install if there is already a default one. it prompts for a short string (like Pd-0.54-0-(alt) to be used to name the install folder, start menu folder, desktop shortcut and uninstall name.

Tested to work correctly on WinXp(i386) and Win11(amd64).

See:: pure-data#2067 (comment)

Closes: pure-data#2073