Compile-time option to allow some prompts remember the input

Define EDIT_GETLIN to make the tty, X11, and Qt4 windowports to
remember the input strings for wishing and annotation.

src/mail.c

@@ -691,7 +691,7 @@ struct obj *otmp;
 {
 #ifdef SHELL /* can't access mail reader without spawning subprocess */
     const char *txt, *cmd;
-    char *p, buf[BUFSZ], qbuf[BUFSZ];
+    char *p, buf[BUFSZ] = DUMMY, qbuf[BUFSZ];
     int len;
 
     /* there should be a command in OMAILCMD */