[diff] IDEA-102751 Don't fail if line separator is unknown.

* Log the error, since it looks that line separator was identified
incorrectly by the LineTokenizer, and we want to investigate it further.
* But return the valid value.
* Escape separators when writing to the log.
Vcs tests: do not ignore IOException in last attempt of clearing directory
fixing http://crucible.labs.intellij.net/cru/CR-IC-277#CFR-32341
Merge remote branch 'origin/master'
IDEA-102584 Conflict resolver run after a Mercurial merge always produce an error

*Change using 'hg log -r "ancestor(r1,r2)" ' to debugancestor command, because  using quotes may produce wrong escaping errors on Unix-type systems.
Subversion command line output parse test: correct paths only for *nix
http://crucible.labs.intellij.net/cru/CR-IC-277#CFR-32315
Merge remote branch 'origin/master'