• Drop gettext / iconv dependencies - they are not used here.
• Drop obsolete THREADS / PCRE / X11 options.
• Convert to OPTIONS helpers.
• Allow to choose between various Kerberos implementations.
• Add Lua 5.2 into supported versions list.
• Restore GTK2 option.
• Improve some descriptions.
• Use 'install_desktop_files' target for installing *.deskop, *.xml and icon files.
• When c-ares is selected, adns will not be used - convert them into OPTIONS_SINGLE.
• RTP support is compiled into GTK+ GUI - disable it in other cases.
• Bump PORTREVISION.

PR: 204411
Submitted by: Andriy Voskoboinyk <s3erios@gmail.com>