- update to 2.1.0
* Improvements and additions:
- Patch #9187 improved the library coverage for the AVR_TINY
architecture (ATtiny10 and relatives). In particular, many
of the functions from are now available there.

- Patch #8729 adds ISR_NOICF and ISR_FLATTEN to
* Bugs fixed:
[#36933] Documentation no longer correctly describes how to declare
[#41689] add static_assert to assert.h
[#48898] power_usart3_* functions no more defined in power.h
[#49020] dtostre() flags documentation error
[#49447] Example code for uart_putchar() has error in recursive call
strings for storage in program memory
[#50439] avr/iom32u4.h does not define PRTIM4
[#51755] iotn441.h & iotn841.h missing definitions for PUEA[0-7] and PUEB[0-3]
[no-id] util/eu_dst.h: fix reversed DST decision logic for March and October
[no-id] util/delay.h.in: add missing return

* Contributed Patches:
[no-id] Define weak symbols for known memory region sizes based on device
header definitions, starting with fuse region.
[#8961] Update test script for new simulavr and library layout
[#8964] Update tests isinf-01.c, signbit-01.c and modf-np.c
[#9163] New eeprom write block function for xmega using eeprom page write
[#8729] [avr/interrupt.h] Add ISR_NOICF, ISR_FLATTEN. Fix namespace
of identifiers.
[#8536] Fix a typo within
[#8649] small documentation fixes in
[#9187] [AVR_TINY]: Support 16-bit xtoa functons and more string functions.
[#9400] Add avrxmega3 multilibs
[#9659] Update eeprom_is_ready for avrxmega3 devices
[#9553] Fix some issues in libc/
[#9864] Use proper float function names and prototypes