This patch supplements each existing connection type with an new
constructor that is meant to replace the original one. The new
one takes a reference to the component's environment as argument and
thereby does not rely on the presence of the globally accessible
'env()' interface.
The original constructors are marked as deprecated. Once we have
completely abolished the use of the global 'env()', we will remove them.
Fixes#1960
This patch changes the top-level directory layout as a preparatory
step for improving the tools for managing 3rd-party source codes.
The rationale is described in the issue referenced below.
Issue #1082
