commands: convert K&R function definitions to ANSI C

Convert the old-style (K&R) function definitions in commands/ to ANSI C
prototypes, formatted in the project's convention: the return type on its
own line and each parameter on its own line, indented four spaces, with
the original parameter comments retained.

Builds cleanly under GCC 16 / C23 (with the -std=gnu17 build change).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

commands/CmdCD.c

@@ -1138,7 +1138,7 @@ CmdCellname(
     int option;
     int locargc = cmd->tx_argc;
     char *cellname = NULL, *orient = NULL;
-    void (*func)();
+    void (*func)(char *, int, bool);
     CellDef *newDef, *cellDef;
 
     static const char * const cmdCellOption[] =