pgm_read_ptr() is wrong in pgmspace.h

[terrillmoore]

The Time library was recently updated to use pgm_read_ptr(). This reveals that the definition in our BSP is wrong.

It is:

ArduinoCore-samd/cores/arduino/avr/pgmspace.h

Line 106 in 81de62e

#define pgm_read_ptr(addr) (*(const void *)(addr))

But it should be:

#define pgm_read_ptr(addr) (*(const void **)(addr))

We need to patch and make a release (v2.3.1, I think, as this is just a bug fix). The test is compiling the LMIC's network-time example with the 4450.