Merge pull request adafruit#1339 from dhalbert/3.x-frozen-swap

Merge 3.x .frozen and /lib swap on sys.path; update frozen libs

Merge pull request adafruit#1314 from dhalbert/3.x-frozen-before-lib

3.x: put .frozen before /lib in sys.path; update frozen libraries

Merge pull request adafruit#1278 from dhalbert/update-frozen-for-alpha.2

Update frozen libraries for 4.0.0-alpha.2

Merge pull request adafruit#1204 from tannewt/merge_3x

Merge in AudioOut fix from 3.x

Merge pull request adafruit#1202 from tannewt/wrong_playback_frequency

Clock the SAMD21 much faster so it can actually convert at its max

Merge pull request adafruit#1186 from dhalbert/uart-enhancements

UART enhancements

Merge pull request adafruit#1131 from tannewt/hallowing3

Support Hallowing in 3.x

Merge pull request adafruit#1036 from hathach/fix_nrf52840_serial

Fix nrf52840 serial mentioned adafruit#1021

Merge pull request adafruit#1006 from dhalbert/3.x-fix-pull

must set pull after setting direction with gpio_set_pin routines

Merge pull request adafruit#986 from tannewt/include_rtc_fix

include RTC fix for SAMd51 in circuitpython build