devel/cdecl: update to 18.4
C++26
Initial support for C++26 has been added, specifically = delete("reason") is now supported.
However, since C++26 is (at least) 2 years away, the default language for C++ is still C++23.
Placemarker for empty macro argument
Macros that can take a single argument can also accept no arguments since it's interpreted as an argument of a placemarker, e.g.:
cdecl> #define M1(A) [A]
cdecl> expand M1()
M1() => [A]
| A => |
M1() => []
is correct.