state of sample code

[bbbart]

So, as an overview, here's the current state of the sample code in the documentation with regards to the upstream samples:

• most work perfectly fine, except for the ones listed below
• convolution_reverb seems to work fine, but the audible result sounds different to my ears when ran from bare C++ compared to through pyfmodex
• dsp_inspector works fine on the parameter level, but shows jumbled data on the DSP level
• record_enumeration is giving an error in the defined callback: userdata seems to be None instead of a pointer to a c_int; I'm actually sure this worked perfectly fine before, so it seems this was introduced in one of the 10th May 2021 commits

Despite their shortcomings, these three are still included in the documentation for the moment.

dsp_custom is not included at all, due to a problem related to adding two parameters to a user defined DSP (see #34 - early comments).

(I can use help in getting these issues above fixed/tested.)