Implement built in fixed point types like was done for floating point

[JulianKemmerer]

See float_e_m_t types and allows different exponent and mantissa widths.

Built in like float, etc...

[JulianKemmerer]

Moving this to Discussions: how C should get fixed-point types is a design question. Pypeline provides them as a library (make_fixed_t in include/pypeline/fixed_point.py).