account for automatic code transformation, generate documentation

[haxscramper]

Due to the nature of the problem, some convoluted code transformation procedures are required, like merging whole analyzed source code in graph and extracting elements back again. Automatic renames, dropped enum values due to nim requirements and so on result in the API that is different from the original one. These differences must be automatically accounted for, and final produced documentation should make it clear how to use the library for someone who is already familiar with Cxx counterpart.

• Re-export types from merged modules. Keep track of what file provided forward declarations and which ones contained real one, and re-export documentation only from the latter.
• Dropped enum value duplicates
• Unspecified default template parameters