[WIP] meson: rework the programmer selection

This is a WIP implementation for a new programmer selection. It should
work by now but has some known and unknown bugs. (see Gerrit Comments)

- Each dependency is optional and gets mandatory when the programmer is
  selected as active.
- Each programmer is defined through an entry in the programmer
  dictionary
- The entry lists systems & cpu_families where the programmer is
  supported; Dependencies, sources and flags. The group parameter is for
  selecting a set of programmer, the default parameter is to include the
  programmer to the `all` and `auto` set.
- If the programmer gets selected the `active` entry is set to true.
  The `active` entry can be used afterwards to determine if the
  programmer should be included in sources, config, documentation
- Needed system headers are represended through a pseudo dependency.
- The programmer's `srcs` attribute contains all files which are needed
  to build the programmer.

Change-Id: Ib44b26e3748fc71f116184082b4aed0bb208b4c1
Signed-off-by: Thomas Heijligen <thomas.heijligen@secunet.com>
---
M meson.build
M meson_options.txt
2 files changed, 413 insertions(+), 337 deletions(-)