STY: minor PEP8 fixups for numpy/fft.
BUG: Fix bugs in unused code paths.

The `getargspec` needed to import the disassembler to support parsing
tuple arguments. Since numpy never uses those, the corresponding code
is deleted and an TypeError raised if such arguments are encountered.

Also fix the unused formatargs function so it does not require the
string module.
STY: Minor PEP8 fixes.
BUG: Fix NaN handling in npy_ObjectMax and npy_ObjectMin.

These functions currently fail randomly for Python < 3.x because they
use PyObject_Cmp, which looks at addresses for NaN objects. The fix is
to use PyObject_RichCompareBool, which is available in Python >= 2.6.
Note that for Python 2.6 and 2.7, PyObject_RichCompareBool falls back on
PyObject_Cmp when an object doesn't provide rich compare.

Closes #4903.
TST: Add tests for maximum/minimum of object arrays with nan.

There is a random element to these tests, so that they may fail to
fail when python compare is being used instead of richcompare.
Merge pull request #4941 from charris/fix-numpy-compat-_inspect

Fix numpy compat  _inspect
Merge pull request #4982 from charris/gh-2941

Fixup of PR #4921
Merge pull request #4936 from charris/pep8-numpy-fft

STY: minor PEP8 fixups for numpy/fft.