m_connflood Ignore e-lined users
m_permchannels Load channels from the config only at module load time and only when there are no linked servers to avoid desync
m_spanningtree Fix incoming channel modes being lost for 0-user permanent channels on the losing side of a netmerge

This did not affect listmodes
Add support for mandatory tags in included config files

If the mandatory tag is not found in the included config, the rehash is aborted. This is especially useful for remote includes, as it allows users to have a dummy tag at the end of the included config to indicate that the config has been wholly read.
This method does not depend on exit codes so even situations where wget returns an empty or a wrong page that we would otherwise accept can be detected and an error can be generated before we assume that the contents have disappeared (and unload all modules, if the included file is supposed to contain module tags, for example).

Usage: <include ... mandatorytag="namehere"> - if the included config doesn't contain a <namehere> tag then the rehash is aborted

Fixes #30 reported by @Justasic
Fix infinite loop when all DNS request slots are in use

This is not the best way to detect this scenario, a better detection mechanism will replace this in the future