Preparation for AIPerService::checkBandwidthUsage.

Don't pass arguments to wantsMoreHTTPRequestsFor, but use globals in
llmessage: AIPerService::sHTTPThrottleBandwidth125 and
AIPerService::sNoHTTPBandwidthThrottling instead.

This is needed later on.
Moved a part of AIPerService::wantsMoreHTTPRequestsFor to a new function.

The new function is AIPerService::checkBandwidthUsage.
No functional changes were made.
Add HTTP bandwidth throttling for every other responder.

Most notably getMesh (the only one possibly using any significant
bandwidth), but in general every type of requests that just have to
happen anyway and in the order they are requested: they are just passed
to the curl thread, but now the curl thread will queue them and hold
back if the (general) service they use is loaded too heavily.
Fix initialization list order (compiler warnings)