The ntptime module was previously only included in the ESP8266 port. This
commit factors that module out into the extmod directory, makes it support
different epochs, and includes it in the rp2 port.
Move webrepl support code from ports/esp8266/modules into extmod/webrepl
(to be alongside extmod/modwebrepl.c), and use frozen manifests to include
it in the build on esp8266 and esp32.
A small modification is made to webrepl.py to make it work on non-ESP
ports, i.e. don't call dupterm_notify if not available.
When loading a manifest file, e.g. by include(), it will chdir first to the
directory of that manifest. This means that all file operations within a
manifest are relative to that manifest's location.
As a consequence of this, additional environment variables are needed to
find absolute paths, so the following are added: $(MPY_LIB_DIR),
$(PORT_DIR), $(BOARD_DIR). And rename $(MPY) to $(MPY_DIR) to be
consistent.
Existing manifests are updated to match.
Ian Davies
Jim Mussared
Damien George