PDOH preprocessor

The PDOH (Parse DynObj Header) preprocessor takes a C++ input file, parses it and generate C++ souce code. This generated code can be inserted into the same file (the usual case), it can be saved to another file, or just printed on stdout.

The purpose is to generate most of the glue code needed to create and use plugins. This includes the type information that is used across the plugin boundary, and the a library skeleton, which is used to instantiate objects.