Use stol instead of sscanf

Author: Matt Kline

docopt_value.h

@@ -13,7 +13,6 @@
 #include <vector>
 #include <functional> // std::hash
 #include <iosfwd>
-#include <cstdio> // sscanf
 
 namespace docopt {
 
@@ -261,12 +260,9 @@ namespace docopt {
 		// Attempt to convert a string to a long
 		if (kind == Kind::String) {
 			// Doesn't guard against trailing characters,
-			// but doing so (if desired) would be trivial.
-			long ret;
-			if (sscanf(variant.strValue.c_str(), "%ld", &ret) == 1) {
-				return ret;
-			}
-			// else fall through
+			// but doing so (if desired) would be trivial by checking pos.
+			std::size_t pos;
+			return stol(variant.strValue, &pos); // Throws if it can't convert
 		}
 		throwIfNotKind(Kind::Long);
 		return variant.longValue;