Centrally decide which hardware UARTS are available

Before, this decision was made in few different places, based on
sometimes different register defines.

Now, HardwareSerial.h decides wich UARTS are available, defines
USE_HWSERIALn macros and HardwareSerial.cpp simply checks these macros
(together with some #ifs to decide which registers to use for UART 0).
For consistency, USBAPI.h also defines a HAVE_CDCSERIAL macro when
applicable.

For supported targets, this should change any behaviour. For unsupported
targets, the error messages might subtly change because some checks are
moved or changed.

Additionally, this moves the USBAPI.h include form HardareSerial.h into
Arduino.h and raises an error when both CDC serial and UART0 are
available (previously this would silently use UART0 instead of CDC, but
there is not currently any Atmel chip available for which this would
occur).

0 files changed, 0 insertions, 0 deletions