Fix a couple of issues with our key parsing / validating code.

- be explicit and expect only ssh-dss or ssh-rsa keys
- allow any character (even line breaks and whitespace) in the optional comment,
  but shrink all of them to simple spaces (fixes issue 679)
- test the newly uploaded key against existing keys only by the base key data,
  not the fully uploaded string (that might contain a changed comment line or
  the like) to avoid duplicates; also only check the keys of the user for
  duplicates, not all existing keys in the forge (if for whatever reason two
  user accounts share a key)

src/IDF/Key.php

@@ -80,7 +80,7 @@ class IDF_Key extends Pluf_Model
         if (preg_match('#^\[pubkey ([^\]]+)\]\s*(\S+)\s*\[end\]$#', $this->content, $m)) {
             return array('mtn', $m[1], $m[2]);
         }
-        else if (preg_match('#^ssh\-[a-z]{3}\s(\S+)(?:\s(\S*))?$#', $this->content, $m)) {
+        else if (preg_match('#^ssh\-(?:dss|rsa)\s(\S+)(?:\s(.*))?$#', $this->content, $m)) {
             if (!isset($m[2])) {
                 $m[2] = "";
             }