Move system_properties over to C++.

This change constitutes the minimum amount of
work required to move the code over to C++, address
compiler warnings, and to make it const correct and
idiomatic (within the constraints of being called
from C code).

bug: 13058886

Change-Id: Ic78cf91b7c8e8f07b4ab0781333a9e243763298c
4 files changed