Compile as C++

[THQ-WIFA]

Is your feature request related to a problem? Please describe.
My compiler offers the option to compile files as C or C++ by file ending (.c/.cpp).
However, there are legacy projects where everything is simply compiled as C++.

Describe the solution you'd like
Trice should be compilable as C++ without warnings.

Measures
I have identified a few measures to take:

• Make casts to/from void* explicit.
• Move two standard library #include within trice.h, to avoid catching them in extern "C" { .... }.

[rokath]

solved with accepted PR #609