Blender Git Loki

Blenkernel: Move node.c to C++

Required changes to compile `node.cc` with clang tidy:
* Use c++ includes like (e.g. climits instead limits.h).
* Insert type casts when casting from `void *`.
* Replace `NULL` with `nullptr`.
* Replace typedef statements.

This change is in order to use the `blender::Map` data structure
for node error messages.