cmake: Support configuring executables for Orocos

Instead of forcing the ADD_EXECUTABLE() and INSTALL() calls on the user,
this allows them to configure an existing executable. This also supports
configuring tests that require Orocos.
Revert "tlsf: use safer init detection flag."

This reverts commit e2327e0fe1d0e07d5a8c3d1175a06999d97319a2. This commit prevents the use of multiple memory pools, (only accessible through the free/malloc_ex).
tlsf: use the first initialized memory pool as the static memorypool, to avoid corrupting previously allocated memory

Signed-off-by: Ruben Smits <ruben.smits@intermodalics.eu>
tlsf: add unit test for tlsf

Signed-off-by: Ruben Smits <ruben.smits@intermodalics.eu>