As some of these are not supported in C++
Additionally, trim DEBUGFLAGS down to focus optimisation level
and debug symbol level only, as --enable-werror will enable
all of the warning flags that will ever be needed

- Define new CFLAGS in debug mode:
  - enable full embedding of debugging symbols
  - lower optimisation to avoid 'jumping' in gdb
  - enable stricter compiler warnings
- mitigate compiler warnings in client example
- Build client and server executables as binaries to
  allow them to be invoked directly by gdb