Manually register GMCP module IRE.Target

This allows the user to re-use mudlet sessions. It is needed because gmod:
a) registers its reenableModules() to the sysConnectionEvent which is too early (no gmcp negotiation yet)
b) is buggy for mudlet 2.1: reenableModules() uses Core.Supports.Set to register modules which breaks modules not set by gmod. (e.g. Modules registered by mudlet itself)