vty: Address compiler warning about tolower
Include ctype.h to have a declaration of tolower.
utils.c: In function 'vty_cmd_string_from_valstr':
utils.c:95:6: warning: implicit declaration of function 'tolower' [-Wimplicit-function-declaration]
diff --git a/src/vty/utils.c b/src/vty/utils.c
index abf0ac4..e9c0d2d 100644
--- a/src/vty/utils.c
+++ b/src/vty/utils.c
@@ -23,6 +23,7 @@
#include <stdint.h>
#include <inttypes.h>
#include <string.h>
+#include <ctype.h>
#include <osmocom/core/linuxlist.h>
#include <osmocom/core/talloc.h>