Behave like Basic's Horizontal and Vertical commands. Internal dline()
optimizations are renamed gint_dhline() and gint_dvline().
Also supports ghline() and gvline() in the gray engine.
Optimization cases here are amost negligible due to limiting RAM access
frequencies and the very limited amount of work accomplished in the
functions. Code maintainability is prioritized by using dline().
This change finally introduces gray image rendering with bopti. This
is the final iteration of bopti v2 and certainly the fastest so far.
All four profiles are supported, without change to the format.
Lephe
lephe