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
chore, allow mex.h to be in include path right away, or in octave_CFLAGS/octave/
Merge branch 'bld/dist'

* bld/dist:
  chore, allow mex.h to be in include path right away, or in octave_CFLAGS/octave/
  fix, PEBKAC, octave-config gives directories, add compiler/linker flags ourselves
  chore, never check for octave with pkg-config ...