graphics/darktable: Update to 2.0.1

darktable 2.0.x officially dropped support for i386. I believe the crash
reported in PR 202457 was specific to 32-bit because this was already
largely untested with darktable 1.6.x, so I'm considering this issue
"fixed".

PR: 202457
Reviewed by: kwm
Approved by: kwm
Differential Revision: https://reviews.freebsd.org/D4247