cartoon should show abutting helices as separate instead of continuous

[Elaine Meng]

I.e. should show a short coil-type connector from the last CA of the first helix to the first CA of the adjacent helix, even though there aren't any residues between them. The continuous depiction generally looks bad since the orientation gets wacky. There are many examples, but to be specific, there are several cases in 4hhb and 5e6z.

Here are some of the ones in 5e6z:
HELIX 5 AA5 ARG A 310 GLY A 313
HELIX 6 AA6 THR A 314 ALA A 328
[...]
HELIX 10 AB1 ASN A 482 LEU A 495
HELIX 11 AB2 ASP A 496 HIS A 503
HELIX 12 AB3 HIS A 504 ASN A 514
HELIX 13 AB4 TYR A 515 GLU A 517

These also cause problems for "tube" helix mode, and maybe fixing this issue will fix the previously reported tickets, because they occur in these same places in 5e6z:

#553 tube stripes
#551 tube armadillos

[Elaine Meng]

Incidentally, in this same structure 5e6z, chain A helix 6 listed above is crazy in the "wrap" mode. I'll attached an image showing chain A residues 300-340, with helix 5 (310-313) colored cyan and helix 6 (314-328) colored yellow. If I change back to the default mode, however, this helix looks fine.

[Conrad Huang]

Adjacent helices now connected by a turn-like one-residue segment in all helix modes (tube, wrap, default).