Don't accept trailing characters when validating numbers for --format

strtoull succeed when the leading characters of the input form a valid
number, so it is necessary to verify that there is no trailing
characters. Use the endptr parameter (that will point to the end of
the accepted input) to verify that.

Fixes #142.

Signed-off-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>

src/globals.c

@@ -301,10 +301,11 @@ int set_version_url(char *url)
 static bool is_valid_integer_format(char *str)
 {
 	unsigned long long int version;
+	char *endptr = NULL;
 	errno = 0;
 
-	version = strtoull(str, NULL, 10);
-	if ((errno < 0) || (version == 0)) {
+	version = strtoull(str, &endptr, 10);
+	if ((errno < 0) || (version == 0) || (endptr && *endptr != '\0')) {
 		return false;
 	}