basic/parse-util: add helper to parse bounded unsigned values

"parse_range" is already used for stuff like "a-b", so use "bounded" here to
avoid confusion.

src/basic/parse-util.h

@@ -30,11 +30,12 @@ int parse_fd(const char *t);
 #define SAFE_ATO_MASK_FLAGS(base) ((base) & ~SAFE_ATO_ALL_FLAGS)
 
 int safe_atou_full(const char *s, unsigned base, unsigned *ret_u);
-
 static inline int safe_atou(const char *s, unsigned *ret_u) {
         return safe_atou_full(s, 0, ret_u);
 }
 
+int safe_atou_bounded(const char *s, unsigned min, unsigned max, unsigned *ret);
+
 int safe_atoi(const char *s, int *ret_i);
 int safe_atolli(const char *s, long long int *ret_i);