Loading shared libraries with appended decorations hides actual errors in case of failure

[anonymous]

When loading a shared library with the boost shared_library class from dll module using the boost::dll::load_mode::append_decorations mode and the loading fails for some reason, the function tries to load the library without decorations. If this also fails because the decorations are mandatory to be appended, the original error of the first (failed) load attempt is hidden, i.e. in the thrown exception, only the error with failed loading due to not found file is visible.

Better would be when the loading without appended decorations would be done only in case the boost::dll::load_mode::append_decorations mode is not applied.

[John Maddock]

Moved to ​https://github.com/boostorg/dll/issues/19