Send the correct version string to InspIRCd servers

This is already the behavior in the 7.1 branch including 7.1.0 as of 1889c0cb96d668233a9655a4113c0958c9804e6f, but this is a better implementation. The 7.1 patch, being developed near the final release of 7.1.0, was self-contained on purpose to not affect the rest of atheme, while this one changes the interface to avoid code duplication.