c++: kconfig: Fix choice dependencies and use 'menuconfig' symbol

 - Make the 'C++ Standard' choice depend on CPLUSPLUS, so that it only
   shows up when C++ support is enabled.

   Also check that CPLUSPLUS is enabled before checking the standard in
   the top-level CMakeLists.txt, to avoid triggering an assert.

 - The 'C++ Options' menu now contains just CPLUSPLUS and its indented
   children. Remove one menu level by removing the menu and turning
   CPLUSPLUS into a 'menuconfig' symbol. Also change the prompt from
   "Enable C++ support for the application" to just "C++ support for the
   application", to make it consistent with e.g. "Logging".

 - Factor out the common CPLUSPLUS dependency with an 'if CPLUSPLUS'.

 - Order symbol properties more consistently with other Kconfig files,
   with the prompt at the top, etc.

Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>
2 files changed