Remove outdated Automake on Windows support.

This didn't work for some time now.
Require C++11 compiler in Unix builds.
Fix unused vars warnings.
Fix dump-legacy-tm tool on Unix.

There was a mismatch between the path in code and in makefiles.
Fix Unicode literals to be wide strings.
Cosmetic fixes for GTK+ version.
Update to use GtkSpell3.

Update the code to require GTK+ 3 and GtkSpell 3 for spellchecking on
Unix.
Misc Unix makefiles fixes.
Use boost::regex with GCC.

GCC's libstdc++ doesn't implement std::regex until 4.9, even though it
does provide the headers.
Fix auto-completion of languages popping up initially under GTK+.
Fix generic wxTextCtrl::SetHint() behavior.

Always skip events that shouldn't be eaten.  Not doing so broke
SetHint()'s generic implementation.
Update Danish translation.