Unnecessary copyin() commands

[LinhWuerzburger]

see #70

[LinhWuerzburger]

by adding

#ifdef _OPENACC
   #include "accel.h"
#endif

and

#ifdef _OPENACC
    acc_present_dump();
#endif

presentcounter in present table dump of OpenACC raises by 1

[LinhWuerzburger]

Depending on which constructor is called the copyin is necessary. Although in case it was already copied the copyin overwrites the new values on the GPU with the old values of the CPU.