armadillo 3.920.2

Closes #418
Revert unintentional regression of samtools

Revert commit 4bf16eb80cd9e09a05a3c69b07c6a1848c1e7e2e
armadillo 3.920.2
armadillo 3.920.2

Closes #418
octave: patch unordered_map bug in configure

Patch to configure, due to a bug in configure.ac, where the ability to
use std::unordered_map as opposed to std::tr1::unordered map was
incorrectly tested, breaking the build on OS X 10.9.

Closes #414
octave: Incorporate upstream patch for std::unordered_map detection.

Follow-up #414.