GCC 4.4 compatibility: local types are not allowed as template arguments.
GCC 4.4 compatibility: need to explicitly list template args for emit().

This is the first (and hopefully only one) ugly thing the user must do
when porting to older GCC.
Interconnect: renamed internal functions to not clash with public ones.

They showed in compiler error messages when connect() was written badly,
which is not wanted at all.
Interconnect: cleaner internal implementation of SignalData.

It is now stored as array of std::size_t which makes it faster for
comparison (only two comparisons instead of 16) and less magic for
hashing, as we can take the value directly.
Merge branch 'master' into compatibility
Qt is not needed as dependency anymore.