nexgb: post-merge fixups and cleanups

AUTHORS, CONTRIBUTORS: still useful, add people from git log, clean up.

LICENSE: Google doesn't really grant you shit anymore.  The EU doesn't
have software patents either, so it doesn't affect me directly.

README, doc.go: erase mentions of unmaintained xgbutil.

nexgb/conn.go

@@ -1,4 +1,4 @@
-package xgb
+package nexgb
 
 /*
 conn.go contains a couple of functions that do some real dirty work related
@@ -138,7 +138,7 @@ func (c *Conn) dial(display string) error {
 		}
 	}
 
-	display = display[colonIdx+1 : len(display)]
+	display = display[colonIdx+1:]
 	if len(display) == 0 {
 		return errors.New("bad display string: " + display0)
 	}