BUG/MINOR: tools: Reject size format not starting by a digit

parse_size_err() function is now more strict on the size format. The first
character must be a digit. Otherwise an error is returned. Thus "size k" is
now rejected.

This patch must be backported to all stable versions.

src/tools.c

@@ -2304,6 +2304,9 @@ const char *parse_time_err(const char *text, unsigned *ret, unsigned unit_flags)
 const char *parse_size_err(const char *text, unsigned *ret) {
 	unsigned value = 0;
 
+	if (!isdigit((unsigned char)*text))
+		return text;
+
 	while (1) {
 		unsigned int j;