As discussed on the mailing list, Barton says we shouldn't check to
see if abs_integrate is loaded when computing integrals of the form
trig(n*x)*trig(m*x) where trig is one of sin or cos.
Fix #4265: integrate(sin(n*x)*sin(m*x),x,0,2*%pi) is always 0
integrate(sin(n*x)*sin(m*x),x,0,2*%pi) is 0 except when n=m. To fix
this, we ask the user if n=m. We also handle the integrands
cos(n*x)*cos(m*x) and cos(n*x)*sin(m*x).
However, this breaks abs_integrate when it is loaded. So, if it is
loaded, we don't ask the user in these cases.
The code in `monstertrig` that applied the substitution `y=c*x+b` was
to fix an issue with integrating `x*sin(n*x)` which used to take
longer and longer as the integer `n` became larger.
However, it appears this is no longer the case. As mentioned in
[#4257], even really large numbers are integrated instantly.
Remove this code. And add a test for this in rtest15.mac
Improves line clippling in Xmaxima's plot2d
Some points that were being left out are now included and the code
can now be used to do clipping with the actual points or with their
representations on the screen.
