ENH: signal: Allow upsweeps of frequency in the 'hyperbolic' chirp.

The restriction that f0 > f1 > 0 has been removed.  The only requirement
is that f0 and f1 are not zero.  Negative frequencies can be given.
(Even f0 and f1 with opposite signs are allowed, but this is not expected
to be a useful case.)  The degenerate case with f0 == f1 is now also
handled.

Two small changes not directly related to the above change:
* Changed "geometric" to "logarithmic" in the argument of the ValueError
  that can be raised when method="logaithmic".
* Added `t = asarray(t)` in the function _chirp_phase, so the 't' argument
  of `chirp` is now `array_like`.

Closes gh-3285.
MAINT: fftpack: Remove the use of 'import *' in a couple test files.
Merge pull request #3378 from WarrenWeckesser/remove-import-star

MAINT: fftpack: Remove the use of 'import *' in a couple test files.
Merge pull request #3367 from pv/splu-bugfix

BUG: sparse/dsolve: fix dense matrix fortran order bugs in superlu wrappers
Merge pull request #3293 from WarrenWeckesser/signal-chirp-hyp

ENH: signal: Allow upsweeps of frequency in the 'hyperbolic' chirp.
ENH: Efficient interpolation on regular grids in arbitrary dimensions
ENH: add fill_value and bounds_error to RegularGridInterpolator
TST: test for equivalence of RegularGridInterpolator and qhull-based ND-interpolators
ENH: add new convenience method scipy.interpolate.interpn
use old-style string formatting to support python 2.6
ENH: support fill_value and bounds_error in interpn
STY: rename kwarg 'kind' to 'method'
ENH: interpolate: uniform xi input arg handling for griddata and interpn
TST: interpolate: add tests for interpn with 1-D xi and xi broadcasting
ENH: interpolate: allow nonscalar-valued values in RegularGridInterpolator
TST: interpolate: reduce code duplication in regulargridinterpolator tests
BUG: interpolate: fix up and test passing in lists to interpn/RegularGridInterpolator
TST: interpolate: test that complex-valued data is handled by rectangulargridinterpolator + interpn
DOC: interpolate: document interpn/RegularGridInterpolator return values