adduser/addgroup: check username for invalid chars
(by Tito <farmatito AT tiscali.it>). +129 bytes when enabled.
diff --git a/include/libbb.h b/include/libbb.h
index d059ac9..19b3bba 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -637,7 +637,11 @@
void clear_username_cache(void);
/* internally usernames are saved in fixed-sized char[] buffers */
enum { USERNAME_MAX_SIZE = 16 - sizeof(int) };
-
+#if ENABLE_FEATURE_CHECK_NAMES
+void die_if_bad_username(const char* name);
+#else
+#define die_if_bad_username(name) ((void)(name))
+#endif
int execable_file(const char *name);
char *find_execable(const char *filename);