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.