lang/duktape and lang/duktape-lib: Update to 2.6.0

• Use CC and CFLAGS from ports framework
• Don't install debug library
• Bump PORTREVISION of www/edbrowse (has lang/duktape-lib as dependency)

Changelog: https://github.com/svaarala/duktape/blob/master/releases/releases.yaml

PR: 250358, 250359
Submitted by: Daniel Engberg <daniel.engberg.lists@pyret.net>
Approved by: arrowd (mentor)
Differential Revision: https://reviews.freebsd.org/D26881