Clean up of warnings (tested on clang).

I tried to cleanup all of the warnings for implicit conversions. I understand that it can be a non-trivial task, for the formability issues related to type conversion can be hard to spot at a first look on the code. For this reason, I am not 100% sure I've done all the necessary edits to your code.
Nonetheless, I think that checking and cleaning up type conversion warnings would be a desirable task, giving users some larger confidence in the code reliability.

Of course, thanks for sharing such a helpful piece of software.

 
Unfortunately this could break the code- see below we memcpy into datapeek_ssz using a length of sizeof(uint32_t). This is one of the operations that go between the serialized tpl image and memory. The serialized format uses explicit fixed sizes so the code uses the same explicit types when copying in/out of the image.