This CL adds C & C++ wrappers and associated tests. Those use default
configurations for a Scudo combined allocator that will likely be
tweaked in the future.
This is the final CL required to have a functional C & C++ allocator
based on Scudo.
The structure I have chosen is to define the core C allocation
primitives in an .inc file that can be customized through defines.
This allows to easily have 2 (or more) sets of wrappers backed by
different combined allocators, as demonstrated by the Bionic
wrappers: one set for the "default" allocator, one set for the "svelte"
Currently all the tests added have been gtests, but I am planning to
add some more lit tests as well.