Fixes segfaults caused by API change. The API change in
lammps_open and lammps_open_no_mpi makes them return the LAMMPS pointer
via their return value. However due to how ctypes operates, even
if restype is specified to be c_void_p, the function returns an integer.
Without the proper type of the pointer, calling functions without arglists would default
to using 32bit integers to pass an argument, which cuts away parts of the 64bit pointer.
Subsequently, resolving the truncated pointer in the library causes segfaults.
This commit fixes the root cause. But it also highlights the need of specifying
the arglists of all library functions.
Adds the following new library functions:
- lammps_has_style()
- lammps_style_count()
- lammps_stlye_name()
The Info class now also has the following member functions:
- Info::has_style()
- Info::get_available_styles()
this is done supporting the combination of type == 2 with style == 0,
i.e. a local scalar, which is not available in C++ (but there one can
access the compute style data member directly. for the python interface,
the pointer is automatically dereferenced and returned as a c_int.
The library interface was extended to provide direct access to atom data using
numpy arrays. No data copies are made and numpy operations directly manipulate
memory of the native code.
To keep this numpy dependency optional, all functions are wrapped into the
lammps.numpy sub-object which is only loaded when accessed.
