1. Simpson integration for extrusion volume in geng-cyl.awk. 2. Move go() to geng-cyl.awkinc

Simpson integration is better for long segments like in geng-cyl-hexagon.awk
Include some duplicated code from geng-cyl.awkinc
Impl accurate segment h treatment in geng-cyl-hexagon.awk
Move feedrate calculation from send-g0.py to const-flow.awk
Add skip-bad-angles.awk
Add g2dat.awk: preprocessor for gnuplot G-code visualization
Add g2dat.awk: preprocessor for gnuplot G-code visualization
Move feedrate calculation from send-g0.py to const-flow.awk
Forgotten file: add GC-parser.awkinc: G-code parser AWK module
send-g0.py: 1) fix some critical bugs; 2) change input file name cyl.g0 -> cyl.g
skip-bad-angles.awk: minor bugfix, parameter tuning, support E priming offset