Changelog for copilot-c99-3.1.1

2019-12-23 Frank Dedden <dev@dedden.net> * Version bump (3.1.1). * Fixed bug with constant structs and arrays.(#13). 2019-11-22 Ivan Perez <ivan.perez@nianet.org> * Version bump (3.1). * Remove ExternFun (#6). * Fix bug in code generation for local expression (#15). * Implement code generation for labels (trivially) (#14).