(issue143) Only show warning when multiple users exist. This enumerates the ProfileList registry key and looks for SID's starting with S-1-5-21- (like the certificate installer does) and count the users. Only when more then one users are found the warning is shown. Otherwise the nss-installer will be removed.

When linking against a shared nss build the nss installation program
has the following NSS run time dependencies:

 - nssckbi.dll
 - smime3.dll
 - nss3.dll
 - nssdbm3.dll
 - softokn3.dll
 - sqlite3.dll
 - freebl3.dll
 - nssutil3.dll
 - libplc4.dll
 - libplds4.dll
 - libnspr4.dll