Doc updates

Update REQUIREMENTS to reflect compatibility with Varnish 6.0.

re2 compatibility has been tested through 2018-04-01.

No longer using the auto-generated SYNOPSIS.

src/vmod_re2.vcc

 #-
-# Copyright (c) 2016-2017 UPLEX Nils Goroll Systemoptimierung
+# Copyright (c) 2016-2018 UPLEX Nils Goroll Systemoptimierung
 # All rights reserved
 #
 # Author: Geoffrey Simmons <geoffrey.simmons@uplex.de>
@@ -9,8 +9,15 @@
 
 $Module re2 3 Varnish Module for access to the Google RE2 regular expression engine
 
+$Synopsis manual
+
+SYNOPSIS
+========
+
 ::
 
+  import re2;
+
   # regex object interface
   new OBJECT = re2.regex(STRING pattern [, <regex options>])
   BOOL <obj>.match(STRING)
@@ -1185,13 +1192,12 @@ Example::
 REQUIREMENTS
 ============
 
-The VMOD requires the Varnish master branch, and is not compatible
-with any current released versions of Varnish. See the source
-repository for versions of the VMOD that are compatible with other
-Varnish versions.
+The VMOD requires the Varnish since version 6.0, or the master
+branch. See the source repository for versions of the VMOD that are
+compatible with other Varnish versions.
 
 It requires the RE2 library, and has been tested against RE2 versions
-2015-06-01 through 2017-11-01.
+since 2015-06-01 (through 2018-04-01 at the time of writing).
 
 INSTALLATION
 ============