Log Message:
Update to 2020-01-19 version.

Pkgsrc changes:
 * adapt patches
 * If NetBSD platform misses 64-bit atomics, turn off all atomics
   (Trying to just disable BIGNUM fails; workaround suggested by
   Fabrice Bellard)

Upstream changes:
- keep CONFIG_BIGNUM in the makefile
- added os.chdir()
- qjs: added -I option
- more memory checks in the bignum operations
- modified operator overloading semantics to be closer to the TC39
  proposal
- suppressed "use bigint" mode. Simplified "use math" mode
- BigDecimal: changed suffix from 'd' to 'm'
- misc bug fixes