Added macro to allow simpler logic in functions with the need to vsnprintf
Replaced vsnprintf with VAFORMAT pretty much everywhere.
Merge pull request #542 from ShutterQuick/inspircd+printfcleanup

Replaced all the individual vsnprintfing with a macro
Fixup last commit
Start to replace MAXBUF with <limits:maxline>.
Reserve ServerLimits::MaxLine instead of MAXBUF.
Compare to ServerLimits::MaxLine instead of MAXBUF.
Use iostream instead of C-style file operations.
Use InspIRCd::Format instead of snprintf().
Replace some C string operations with the + operator.
Rewrite irc::sockets::sockaddrs::str() completely.

- Replace use of MAXBUF with INET_ADDRSTRLEN/INET6_ADDRSTRLEN.
- Replace use of sprintf with InspIRCd::Format.
Convert ConvNumeric() to use std::string instead of char[MAXBUF].
Convert User::FormatNoticeMasks() to use std::string.
Convert User::SendText to use std::string.