v0.13: Version 0.13

Changelog:

e2d854e appveyor.yml: Downgrade llvm and clang packages for the moment
3131f83 Bump to version v0.13
21e8bf2 network: Fix crash when lots of file descriptors are open
fb5fa69 Revert "RFC: Fix channel identifier heuristics"
19c1f6d local: fix last_dequeued is not invalidated in case of a timeout (blocking) or on retry (non-blocking) buffer
833e532 RFC: Fix channel identifier heuristics
aa49293 appveyor.yml: Copy the README file in the .zip artifact.
c620783 Sync README and appveyor so the README points to the latest master.
e1f420c appveyor.yml: Change the name of the zip artifact.
3ac535b Create zip.txt
6f6ced3 network: Adjust switch statment "fall-through" comment position