Previously mailbox was copying a list of attributes from one message object to
another in order to "copy the message data".  This means that any time new
attributes were added to email.message.Message, mailbox broke.  Now instead it
copies all attributes from the source object to the target object, skipping
any mailbox-object-specific attributes to produce the same clean initial
state it was previously getting by copying only the "known" attributes.

David Lam assisted in the development of this patch.

This avoids crashing the server loop when a signal is received.
Patch by Jerzy Kozera.

This avoids crashing the server loop when a signal is received.
Patch by Jerzy Kozera.

presence of a __del__ attribute on objects, rather it uses the tp_del slot.

Patch by sbt.

types on some platforms.

is defined as an int while everyone else expects a long regardless of
length.

2) Assert that the source operand is not special. Prevent resulting assert
   failure (harmless) by initializing flags before calling mpd_qshiftr_inplace.

3) Save a couple of instructions (mpd_zerocoeff already sets digits and len).
   Reorder initialization to match the order in the mpd_t struct.

Found with Clang's Static Analyzer.

after itself properly.

deadlock if the main thread fails before sending all the data.

Initial patch by Popa Claudiu.

Initial patch by Popa Claudiu.

Patch written by Serhiy Storchaka