Fix some implicit function declarations

Hstrdup.c: missing stdlib.h for exit()
Hstrtoul.c: missing string.h for strcmp()

Author: chrstphrchvz

pTk/config/Hstrdup.c

@@ -1,3 +1,4 @@
+#include <stdlib.h>
 #include <string.h>
 
 #define STRING "Whatever"

pTk/config/Hstrtoul.c

@@ -1,4 +1,5 @@
 #include <stdlib.h>
+#include <string.h>
 
 int main()
 {char *e;