Distutils code needs to run in different temporary directories, probably
because they create `_configtest.c` files for compiler detection in the
current directory.

Previously, f2py loaded the type mappings from a file ``.f2py_f2cmap``
in current directory, at import time.

Make the file name customizable by adding a ``--f2cmap`` command line
option, and postpone loading the file to f2py.run_main().

Moreover, restore the default type mapping in f2py.run_main() before
loading the customizations, so that multiple calls to f2py.run_main() do
not interfere with each other. (For example, numpy.distutils calls f2py
multiple times in the same process.)

BUG: General fixes to f2py reference counts (dereferencing)

A BytesWarning can be emitted when bytes are and strings are mismatched.
Catching BytesWarning ensures a better boundary between str and bytes
type. The test suite is now run with the -b flag to emit this warning.

Fixes #9308

Note that the extension module dict seems to be never dereferenced
(there is an additional reference to it kept around somewhere).
This reference seems to part of the C python module loading
(possibly intentionally), and I could not find how to remove it or
where it originates from.

Using `PyMem_Del` is incorrect, it should be `PyObject_Del` here, while
this worked most of the time, it would lead to crashes at least on python
2.5 (after the reference counts were fixed)

pip will itself call setup.py install with the rights options.