The standard DIM() macro was not typesafe as it happily deferred errors
to runtime that can be caught at compile time. Replacing it with a
generic C++11 constexpr allows for typecasting, comparison and compile
time error checking.
Previously, the M and G00, G01, G02 and G03 commands were read, but nothing was actually done.
The current support is a bit rough, but it allows reading some drill files with routing commands.