Remove duplicate block()/unblock() code

See merge request i4/manycore/emper!11

This makes all EMPER synchronization primitives inherit from
Blockable. As result all block and unblock operations of a context
will go to the same code path. We can later use this to store the set
of currently blocked contexts.

Also Blockable now inherits Logger, which makes some things easier,
but as result we have to invoke the logX() methods with "this->"
prepended. See related code comment.

fix Actor and UnboundedBlockingMpscQueue

See merge request i4/manycore/emper!9

Currently the write to 'state' from stop() is overridden in actorLoop()
if it occurs while the Actor is executing the while loop body in actorLoop()
because the while loop body unconditionally writes 'state'.

To prevent those lost 'state' updates actorLoop() now uses compare_exchange
to switch 'state'.

Not initializing blockedContext means its original value is undefined and
probably some random stack value != nullptr.

If the first put() is executed before the first blocking get(), put() will read a
random value from blockedContext and will call unblock with this random context
pointer leading to execution of random memory.

declare die() as noreturn

See merge request i4/manycore/emper!8

support generic test suites not just 'smoke'

See merge request i4/manycore/emper!7

[meson] export and use meson options as C/C++ defines

See merge request i4/manycore/emper!2

All options in meson_options.txt are exported in emper-config.h as
uppercase defines and prefixed with EMPER_.
Every source file using one of the EMPER_* defines now includes "emper-config.h".

make emper consumable as meson subproject

See merge request i4/manycore/emper!1

The variable names follow the naming convention for dependency variables.
Dependecy variables are needed for emper to be consumed as a meson subproject.
https://mesonbuild.com/Subprojects.html

As localTop may hold the updated value of top after the
compare_exchange failed.

"""
Otherwise, loads the actual value stored in *this into
expected (performs load operation).
"""

Co-authored-by: Nicolas Pfeiffer <nicolas.pfeiffer@fau.de>

to avoid clash with the upcoming emper Semaphore.

To make use of C++17 new operator with alignment support.

As I do no longer use cmake-ide in favor of lsp-mode, those are no
longer required.

because the hook is also invoked on resumption of the, now unblocked,
context.

Fixes a memory leak where the "from"-context would not be freed.