Bug fixes, viper improvements, and more

New features in core:
- min and max accept key= argument
- accepts user defined ==, >, <=, >=
- native support for ARM (non thumb)
- cut RAM and ROM usage of zlibd
- significant GC allocation speed up

Viper improvements:
- type annotations
- store to global
- call functions with native types
- raise exceptions

Bug fixes to core:
- fix multiplication of a sequence by negative number
- GC bug fix where native code was being collected
- int(b'1234') now works
- can now make strings longer than 64k

unix port:
- modtermios for unix
- make install for unix

stmhal port:
- reduced code size by 35k
- put some code into first 16k block
- in safe mode SD card is still presented as MSD
- SD card init fixes; should be more reliable
- added time.mktime; enhanced time.localtime
- new Pin functions: mode, pull, af
- nestable enable_irq/disable_irq
- added pyb.micros()
- added USB_VCP.any()
- STM32F4DISC accel support via staccel.py script