Log Message:
libffcall: update to 2.1.

New in 2.1:

* Added support for the following platforms:
  (Previously, a build on these platforms failed.)
  - x86_64: Solaris 11.3.
  - OpenBSD 6.1.
  - HardenedBSD 10 and 11.

* Fixed a bug regarding passing of pointers on the following platforms:
  - x86_64: Linux with x32 ABI: CC="gcc -mx32".

* Fixed a crash in trampoline on the following platforms:
  - mips: Linux with CC="gcc -mabi=64", little endian.