Merge branch 'master' of https://github.com/cbhaley/calibre
Use TLS 1.2 when available for https
Use a functionality check on the SSL module instead of checking version numbers, since there are distros out there that backport patches without changing version numbers
Save to disk: Fix a regression that prevented saving of files into the root of a drive on windows
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Set Cover Url
Fix Login (httperror_seek_wrapper: HTTP Error 404: Not Found)
Merge branch 'master' of https://github.com/lala-rob/calibre
Workaround for Ubuntu/Debian's brilliant decision to partially backport patches from python 2.7.9 to 2.7.8
Some work on completion for the editor
version 2.13.0
Better error message when startup fails because of singleinstance failing
Report builder errors in stage2 properly
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Prevent sockets launched for IPC communication on linux from being inherited by processes launched from the GUI

Previously only the listen socket was marked as CLOEXEC, now the actual
fd used for communication is also marked as CLOEXEC
Do not use a file for the single instance mutex on linux
Make singleinstance() more robust on OS X

It now handles EINTR and also does not hide all errors in opening the
file or calling lockf()

An error is now reported to the user in a nice error dialog before
aborting startup.
Small perf improvement
More work on the completion worker
Metadata review dialog: Show a confirmation for the "Reject all remaining" button. Fixes #1404386 [Reject All Remaining - Confirmation box please!](https://bugs.launchpad.net/calibre/+bug/1404386)