Close file descriptors on exec

Avoid FD leakage to children.

--- cftoken.c.orig	Sun Jan 10 00:42:37 2016
+++ cftoken.c	Sun Jan 10 00:43:29 2016
@@ -2539,7 +2539,7 @@ cfswitch_buffer(incl)
 	incstack[incstackp].state = YY_CURRENT_BUFFER;
 	incstack[incstackp].lineno = lineno;
 
-	fp = fopen(path, "r");
+	fp = fopen(path, "re");
 	if (fp == NULL) {
 		dprintf(LOG_ERR, FNAME, "cfparse: fopen(%s): %s",
 			path, strerror(errno));
@@ -2562,7 +2562,7 @@ cfparse(conf)
 	char *conf;
 {
 	configfilename = conf;
-	if ((yyin = fopen(configfilename, "r")) == NULL) {
+	if ((yyin = fopen(configfilename, "re")) == NULL) {
 		dprintf(LOG_ERR, FNAME, "cfparse: fopen(%s): %s",
 			configfilename, strerror(errno));
 		if (errno == ENOENT)