Patch by Natalia B. Bidart.

the "flag" argument is "n", dbm.error was being raised. As documented,
dbm.open(...,flag='n') will now "Always create a new, empty database,
open for reading and writing", regardless of a previous file existing.

Without this patch "./configure --with-pydebug --enable-framework CC=gcc-4.0" fails on MacOSX

Patch by Evan Dandrea.

non-semaphore implementation of locks is used under POSIX.

Issue 11131: Fix sign of zero result on decimal.Decimal plus and minus operations in ROUND_FLOOR rounding mode.

Patch by Michal Nowikowski.