Function literals and value closures: proposal for C23

We propose the inclusion of simple lambda expressions into the C standard. We build on a slightly restrictedsyntax of that feature in C++. In particular, they only have immutable value captures, fully specified parameter types, and, based on N2735, the return type is inferred from return statements. This is part of aseries of papers for the improvement of type-generic programming in C that has been introduced in N2638.Follow-up papers N2738 and N2737 will extend this feature with auto parameter types and lvalue captures,respectively