python: Fix -Wunused-parameter

Although the most part of the parameters marked as unused are actually
being used for a few functions, a bunch of warnings can be seen when
the code is compiled with "-Wall -Wextra". As adding the unused attribute
means that the variable/parameter is meant to be *possibly* unused, we're
safe adding it in the generated code, even for used variables/parameters.
python: Fix -Wsign-compare

The return of the get_array_size() is used as a limit in a loop,
being compared with an unsigned index (indexes are always unsigned).
To avoid the -Wsign-compare warning, let's cast the return of the
get_array_size() to unsigned and make GCC happier.
common: Remove dead code
common: Fix -Wunused-parameter
common: Fix -Wsign-compare
common: Fix -Wmissing-field-initializers