tests: for consistent output flush between writing sterr and stdout

Because stdout and stderr are buffered, the order of the output is other way
around on some systems.
import-checker: fix names of dynamically loaded modules

The import checker found standard library modules such as
lib-dynload/zlibmodule.so but saw that as a 'zlibmodule' module, not as the
'zlib' module.

Debian ships Python with most modules built-in and this incorrect handling of
dynamic modules did thus not cause problems on that platform.

Fedora ships Python with as many modules as possible loaded dynamically. That
made the import checker tests fail with incorrect classification of the
following modules: array fcntl grp itertools time zlib.

This change makes test-module-imports.t pass on Fedora.
tests: ignore http tests that are known wontfix failures on python 2.4

As mentioned on http://bz.selenic.com/show_bug.cgi?id=2739#c17 , b3083042bdda
left test-http.t failing on Python < 2.4.3. That has not been noticed because
most 2.4 testing has been done with a patched 2.4.2.

This makes sure that the tests only are run for Python >= 2.4.3. That makes it
possible to verify that everything else works with Python 2.4.
tests: improved test coverage for HTTP authentication and 401 responses

Dump the access log to verify that the client gets the 401s it deserves and
handles them correctly. This establishes a baseline for Basic authentication
protocol.
import-checker: show stdlib and relative imports separately

Make the output more useful for debugging problems.
tests: use small conditional section for tic requirement in test-status-color.t

Better test coverage when curses not is available.
contrib/Makefile.python: build local Python from source

This provides an easy way to install new or old Python versions on Unixish
systems. It is mainly intended for testing Mercurial with different Python
versions.

Example:
  $ cd build
  $ make -f ../contrib/Makefile.python python PYTHONVER=2.4 PREFIX=/tmp/p24
  $ /tmp/p24/bin/python -V
  Python 2.4

Tested on Fedora, Debian and Ubuntu with Python versions from 2.4 to 2.7.6.

Most Python versions need some workarounds to compile on Debian-ish systems.
The workarounds do not do any significant harm on Fedora.