secs2d

Issues:

• oct343 variant didn't build on 10.5, but does on 10.7. Addendum: this appears to have been due to funky octave343 builds, since it worked fine with a freshly built, rather than hacked up, octave343 on 10.5.
• Wants gmsh and dx, the latter of which doesn't exist on 10.7. Addendum: while we work on dx, I've added it to 10.7 without dx support (since it was already present there, anyway).