devel/cdecl: upgrade to 3.1

C++ new-style casts
Added support for C++ new-style casts.

Language-sensitive autocompletion
Autocompletion is now language-sensitive in that it will not offer completions that are not valid in the current language.

Context-sensitive autocompletion
Autocompletion is now slightly more context-sensitive in that it will offer only command keywords for the first word in the input.

Fixed command-line error printing
Command-line input is now printed when there's an error.