bump the trunk version to 0.6+ to differentiate it from the 0.6 branch builds

mail/app/module.ver

@@ -1,8 +1,8 @@
 WIN32_MODULE_DESCRIPTION=Mozilla Thunderbird
 WIN32_MODULE_PRODUCTNAME=Thunderbird
 WIN32_MODULE_NAME=Thunderbird
-WIN32_MODULE_FILEVERSION=0,5,0,0
-WIN32_MODULE_FILEVERSION_STRING=0.5+
+WIN32_MODULE_FILEVERSION=0,6,0,0
+WIN32_MODULE_FILEVERSION_STRING=0.6+
 WIN32_MODULE_COPYRIGHT=©Thunderbird and Mozilla Developers, according to the MPL 1.1/GPL 2.0/LGPL 2.1 licenses, as applicable.
 WIN32_MODULE_COMPANYNAME=Mozilla.org
 WIN32_MODULE_TRADEMARKS=Mozilla