textio: convert K&R function definitions to ANSI C

Convert the old-style (K&R) function definitions in textio/ 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>

textio/txCommands.c

@@ -176,8 +176,8 @@ FD_OrSet(
 
 /* A bitmask find max bit set operation */
 int
-FD_MaxFd(fdmask)
-    const fd_set *fdmask;
+FD_MaxFd(
+    const fd_set *fdmask)
 {
     int fd;
     for (fd = FD_SETSIZE-1; fd >= 0; fd--) /* backwards */
@@ -1841,11 +1841,11 @@ txCommandsInit(void)
  */
 
 bool
-TxLispDispatch (argc,argv,trace, inFile)
-     int argc;
-     char **argv;
-     int trace;
-     int inFile;
+TxLispDispatch(
+    int argc,
+    char **argv,
+    int trace,
+    int inFile)
 {
   TxCommand *cmd = lisp_cur_cmd;
   int i,j,k;

textio/txcommands.h

@@ -38,7 +38,7 @@
 #define	TX_MAXARGS	200
 #define TX_MAX_CMDLEN	2048
 
-typedef struct {		/* A command -- either a button push or
+typedef struct TxCommand_ {	/* A command -- either a button push or
 				 * a textual command.
 				 */
     Point tx_p;			/* The location of the pointing device