Introduce a new client fiber which sends a string to the server fiber
expects an echo.

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.