devel/cdecl: upgrade to new major version 3.1

This version fixes virtually all the deficiencies in earlier versions as well as adds many new features, most notably:

Using GNU Autotools for building.
Command-line long-options.
Distinguishes among K&R C, C89, C95, C99, C11, C++98, C++03, C++11, and C++14.
Support for C11 and C++11 types bool, char16_t, char32_t, complex, restrict, size_t, thread_local, and wchar_t.
Support for inline function declarations.
Support for typedef declarations.
Support for variadic function arguments.
Support for C++11 constexpr, enum class, mutable, rvalue references, and the function trailing return-type syntax.
Support for const, final, friend, override, volatile, virtual, pure virtual, and ref-qualified C++ member function declarations.
Better warning and error messages complete with location information and color.

Take Maintainer'ship.

Submitted by: paul@lucasmail.org
Approved by: adamw (mentor, implicit)