setup 2.902 release candidate - please test

[Jon Turney]

A new setup release candidate is available at:

   https://cygwin.com/setup/setup-2.902.x86_64.exe (64 bit version)
   https://cygwin.com/setup/setup-2.902.x86.exe    (32 bit version)

Please test, and report any problems here.

Changes compared to 2.901:

- Can now verify (using a public key provided with the --pubkey option) 
signatures made:

* using an RSA key

* using a DSA key with an alternate hash algorithm (e.g. 'gpg 
--enable-dsa2 --personal-digest-preferences=sha256' with a 1024D key)

* using multiple keys (i.e. the .sig file contains multiple signatures), 
where a signature from a known key is not the first one appearing.

- Embeds a new Cygwin public key (which nothing is actually signed with yet)

* The '--disable-old-keys' option disables use of the current Cygwin 
signing key.

- When run with the '--no-admin' option, restore output appearing in a 
Cygwin terminal (when using Cygwin 3.1.0 or later)

- Various code cleanups