add extensibility feature for longer periods?

[listx]

I noticed that the CPP version (line 1617 in pcg_random.hpp) of this library has extended generation schemes allowing arbitrary periods (section 7.1 in the paper). Could we add this to this C version as well?

[imneme]

You can get almost the same effect by just ganging together several generators (with distinct streams) as shown in the example code.

But, if someone wants to port the extended generation scheme from C++ to C (probably better to start from scratch than try to remove the C++-isms in the code), I'd certainly be open to merging their changes.