Per default Tslab checks that 8 slabs incl. overhead fit into one block.
If this is not desired the template parameter 'MIN_SLABS_PER_BLOCK' can
be used to control the minimum number of blocks.
Fixes#3834
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