Replaced deprecated cast.hpp with polymorphic_cast.hpp. Droped dependency to the Numeric library
more robust implementation for BOOST_RANGE_EXTRACT_OPTIONAL_TYPE
Merge pull request #10 from apolukhin/develop

Replaced deprecated cast.hpp with polymorphic_cast.hpp. Droped dependenc...
fixed and resolved missing coverage in the copy_backward unit test.
More remove execute attribute from files.

  rel. to:
  https://github.com/boostorg/range/commit/e0e6fefb1ed5e6207428143876f507d45b381891

Signed-off-by: Kohei Takahashi <flast@flast.jp>
Merge pull request #12 from Flast/pr/file-mode

More remove execute attribute from files.
Fixed range adaptors that were creating underlying iterators that were not default constructible.
Merge branch 'develop' - small fixes in addition to a more major fix for adaptors
producing iterators that did not have default constructors.