Inheriting std::iterator is deprecated in C++17

fixed example: iterate all left items

* Add BOOST_COROUTINES_DECL where needed

The resolves warning C4251:

"...needs to have dll-interface to be used by clients of class..."

Fix Windows dll-interface compilation warnings:

Since Boost.System is header-only now, no need to link with the library.

Remove linking with Boost.System

Justinas V. Daugmaudis: This patch prevents abi::__forced_unwind from being eaten

This helps ensure that library inclusion is self sustainable

Fix project names clash

Move library include to the top

Cease dependence on Range

This helps ensure that library inclusion is self sustainable

This reverts commit 0c556bb.

see #44 (One test fails to compile after boostorg/coroutine submodule updated)

This reverts commit a3e511f.

(cherry picked from commit 0203086)

(cherry picked from commit 39db8c4)

I did not notice that begin/end indirectly uses range_begin/range_end.

Use a non-deprecated header

(cherry picked from commit 05e2576)