Backported fixes for Clang and Boost 1.57 from master.
Update ChangeLog and News for version 1.4.1.
Merge hotfix for Boost 1.57 and Clang.
Moved QuantLib version to 1.4.2 on the 1.4 branch.

The QuantLib-SWIG version stays the same (there were no changes
and no release there).
Update download page for 1.4.1 release.