Magicsig::generate is now static

This also fixes a problem with "initial salmon slap", which was a
problem for newly registered accounts which would have their first
salmon slap fail to distribute since there was a problem with Magicsig
keys. Apparently we have to re-read them with importKeys so the
Crypt_RSA objects publicKey and privateKey match later instances of them.

I think it may have been that generate() doesn't specify a signatureMode,
but I leave experimentation of that to the future.

plugins/OStatus/OStatusPlugin.php

@@ -1344,9 +1344,7 @@ class OStatusPlugin extends Plugin
         // Get this profile's keypair
         $magicsig = Magicsig::getKV('user_id', $target->id);
         if (!$magicsig instanceof Magicsig && $target->isLocal()) {
-            // No keypair yet, let's generate one. Only for local users.
-            $magicsig = new Magicsig();
-            $magicsig->generate($target->getUser());
+            $magicsig = Magicsig::generate($target->getUser());
         }
 
         if ($magicsig instanceof Magicsig) {