mseq: use first message of range for -c and -C.

mseq.c

@@ -251,6 +251,9 @@ stdinmode()
 void
 overridecur(char *file)
 {
+	static int once = 0;
+	if (once++)
+		return;
 	while (*file == ' ')
 		file++;
 	setenv("MAILDOT", file, 1);
@@ -259,6 +262,9 @@ overridecur(char *file)
 void
 setcur(char *file)
 {
+	static int once = 0;
+	if (once++)
+		return;
 	while (*file == ' ')
 		file++;
 	unsetenv("MAILDOT");