[fix] Adding stdint.h include to most of the header files for portability

src/numex.h

@@ -8,6 +8,7 @@ extern "C" {
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <stdint.h>
 #include <stdbool.h>
 #include <string.h>
 #include <inttypes.h>