Deep copy support for structs

[amikstcyr]

Hi OCCA-ers,

For non-trivial (read big-ol-mess) codes, it is sometimes necessary to copy structs (which contain also structs or stl containers) to the GPU & back ... (well at least to the GPU :-)). This avoids costly API changes when more than a handful of functions need to "kernel-ized".

Not sure about the flexibility of the current parser but maybe a low-hanging fruit using source to source tricks could be employed?

Best,

Amik

[dmed256]

Structs of structs with basic types (like int/double/nested structs in #141) is probably the next feature to be added, so stay tuned :)

I don't think we can handle pointers in structs easily though, but maybe we can build up another occa::X type that can translate between host <--> device

[dmed256]

@amikstcyr Basic structs are now be available in beec0865857f5fbdf55554deb596396b40614357

Missing:

• typedef-ing structs

  typedef struct { } foo;
  

• Expanding @attributes on struct variables

  struct mat3 {
    int *values @dim(3, 3);
  }
  mat3 m;
  // Error since the parser right now doesn't "know" `values` is a @dim(3, 3)
  m.values(0, 0); 
  

• Access level modifiers are not supported at the moment

  struct foo {
    private: ...
  }