Patch by Akira Kitada.

Patch by Francisco Martín Brugué.

The new wording is based on the comments in the code, which
match the actual behavior.

Locks are implemented using a mutex and a condition variable of the pthread
library on FreeBSD6. POSIX condition variables cannot be interrupted by signals
(see pthread_cond_wait manual page).

Cannot test an empty environment on Windows: Windows requires at least the
SYSTEMROOT environment variable to start Python.

Mac OS X adds __CF_USER_TEXT_ENCODING variable to an empty environment. Fix
also the test on the Py_ENABLE_SHARED config varible: test that the variable is
present, don't check it's value.

Try also to get more informations about the Mac OS X failure: display the keys
of the environment, instead of just the number of variables.

variables, start with an empty environment.

processes if negative or null.

Patch by July Tikhonov.

Analogous to the decode_header fix, this fix makes Header.append and
make_header correctly handle the unknown-8bit charset introduced by email5.1,
when the input to them is binary strings.  Previous to this fix the
make_header(decode_header(x)) == x invariant was broken in the face of the
unknown-8bit charset.

This updates b21fdfa0019c, which fixed this bug incorrectly.

This makes them work like the close provided by regular file objects.