We use tons of plain C-style #defines to give symbolic names to constants all
over the place already, in headers used from C++ code only. So why in this
rare case where the symbolic names for some constants actually would be needed
from a C source file, too, here then we define them inside a C++ class?

Change-Id: I45726fe42687779724c45a1e2b118cc7a1debcf1