What ``cmLocalGenerator::GetIncludeDirectories`` does
-----------------------------------------------------

In general it concatenates the

1. ``target->GetIncludeDirectories(LANG)`` and the
2. ``CMAKE_<LANG>_STANDARD_INCLUDE_DIRECTORIES``.

Additionally it performs some sorting and special treatment of the

- ``CMAKE_<LANG>_IMPLICIT_INCLUDE_DIRECTORIES``.

By default all ``CMAKE_<LANG>_IMPLICIT_INCLUDE_DIRECTORIES`` are stripped from
the result list.

When explicitly requested (by setting ``stripImplicitInclDirs=false``) *some*
implicit directories are appended to the result list.  The implicit directories
that *are* appended are those that were requested to be included by

1. ``target->GetIncludeDirectories(LANG)`` or
2. ``CMAKE_<LANG>_STANDARD_INCLUDE_DIRECTORIES``.

All other implicit directories are still stripped from the result list.

The reason to not simply append all implicit directories is that Qt4's moc has
problems to ...