Fixed build error with VS2015

yhirose · yhirose · commit 9ee03a92110f · 2019-08-27T17:13:27.000-04:00
diff --git a/peglib.h b/peglib.h
@@ -9,6 +9,7 @@
 #define CPPPEGLIB_PEGLIB_H
 
 #include <algorithm>
+#include <cctype>
 #include <cassert>
 #include <cstring>
 #include <functional>
