ComputerSettings: move to src/Computer/

.. and split the header.
InfoBoxes/Task: move "home" to Places.cpp
InfoBoxes/RadialATC: use selected "ATC reference"

.. instead of the next waypoint in the task.  Add attribute
"atc_reference" to struct PlacesOfInterestSettings.  Implements TRAC
#2706, modifying the code that implemented #2269.
test/DebugPort: support the K6Bt
Driver/Volkslogger: fix flightget(), read_igcfile() types
Driver/Volkslogger: move API documentation to header
Driver/Volkslogger: simplify fdf_findfield()

Return instead of breaking; eliminates the variable "ii".
Driver/Volkslogger: make nturnpoints unsigned
Driver/Volkslogger: use "int" for fdf_findfield() return type
Driver/Volkslogger: use "unsigned" for DCLWPT attributes

Using the smallest possible type for this struct has no advantages,
but requires more CPU to convert 16 bit to a machine word.
Driver/Volkslogger: don't return "serno" and "sp" from convert_gcs()

The only caller doesn't need them.
Driver/Volkslogger: pass bool to convert_gcs()
Driver/Volkslogger: remove all data attributes from class VLAPI

These should be managed by the caller on demand.
Driver/Volkslogger: eliminate class VLA_SYS

This was only holding the Port reference.  Move that to VLA_XFR and
turn the pointer into a reference.
Driver/Volkslogger: use size_t for buffer sizes
Driver/Volkslogger: move code to Protocol.hpp
Driver/Volkslogger: remove unused method apiversion()
Driver/Volkslogger: use constexpr instead of enum
Driver/Volkslogger: use one large buffer in class DBB

Eliminates several duplicate I/O buffers.
Driver/Volkslogger: pass const DBB to DECLARATION::get()