fix compilation error in core_io.h

- error: 'vector' in namespace 'std' does not name a type
- add <vector> include in core_io.h
- remove <vector> includes from core_read.cpp and core_write.cpp

src/core_io.h

@@ -2,6 +2,7 @@
 #define __BITCOIN_CORE_IO_H__
 
 #include <string>
+#include <vector>
 
 class uint256;
 class CScript;