chore, never check for octave with pkg-config ...

At least as long as upstream doesn't bother providing a .pc file.
fix, PEBKAC, octave-config gives directories, add compiler/linker flags ourselves
Merge branch 'contrib/mex-tzconv'

* contrib/mex-tzconv:
  fix, PEBKAC, octave-config gives directories, add compiler/linker flags ourselves
  chore, never check for octave with pkg-config ...