Book polishing: Fix EPUB files with corrupted ZIP central directories not working and leaving behind detritus in the current working directory. Fixes #1360385 [Debris left when polish books fails](https://bugs.launchpad.net/calibre/+bug/1360385)
Edit book: Workaround for regression in Qt 5 that causes typing the Cmd+some letter to generate text in the editor instead of being ignored.

https://bugreports.qt-project.org/browse/QTBUG-40933
Note about Qt 5 vs. Windows XP
E-book viewer: Fix Table of Contents open state not being remembered when the remember window size setting is disabled
E-book viewer: Fix a regression in 2.0 that changed the speed of scrolling with the mouse wheel in flow mode
Fix #1360547 ["Legacy" window title](https://bugs.launchpad.net/calibre/+bug/1360547)
Fix the unified title and toolbar on Mac tweak causing calibre to fail to work because of a bug in PyQt5
Workaround for Qt 5 bug that prevents using the return key to edit table cells in the main book list

https://bugreports.qt-project.org/browse/QTBUG-40938
E-book viewer: Fix navigating to a bookmark not updating the displayed page number. Fixes #1360621 [(ebook-viewer) weird behaviour dealing with current page in ePub](https://bugs.launchpad.net/calibre/+bug/1360621)
Linux: Disable the optional system tray icon in linux because of bugs in the system tray icon implementation in Qt 5 on linux. See #1360652 (calibre 2.0 system tray icon missing, cannot quit)

https://bugreports.qt-project.org/browse/QTBUG-31762
pep8
Prevent calibre from installing or running on Windows XP as there have been many reports of Qt 5 crashing on Windows XP and Windows XP is now no longer supported by Microsoft.
Possible fix for --detach crash on some linux systems

Do not use file objects for redirecting the std streams as they could be
garbage collected closing the streams. Also redirect stdin. I dont
really expect either of these to fix the issue, but it's a start.
Use C code to redirect standard I/O streams for --detach and --daemonize
...