This introduces the new macro SAM_D5X_E5X. This is mostly the same
as SAMD51 before, except in a few places where a special case for
SAME54 is required
Before this change, `microcontroller.cpu.uid` returned values
where the top 4 bits of each byte were zero, because of
an incorrect bitmask used in this function.
shared_bindings/index.rst: updated Support Matrix format as discussed in PR #503 & Issue #448.
shared-bindings/microcontroller/Processor.c & .h: added UID lookup functionality for use with all ports. Fixes#462.
