Source Han Sans: A new open source Pan-CJK typeface family from Adobe

This is Source Han Sans TC/TW, which supports all four variants in this family
but prioritizes Traditional Chinese Hanzi over other three.

"Source Han Sans, available in seven weights, is a typeface family which
provides full support for Japanese, Korean, Traditional Chinese, and Simplified
Chinese, all in one font. It also includes Latin, Greek, and Cyrillic glyphs
from our popular Source Sans family. All told, each font weight in the family
has a total of 65,535 glyphs (the maximum supported in the OpenType format), and
the entire family rounds out at just under half a million total glyphs."

• The Typekit Blog, Adobe

WWW: https://github.com/adobe-fonts/source-han-sans

PR: 232187
Submitted by: Hyun Hwang
Approved by: (one of the mentors)

• poudriere (11.2-, 12.0-RELEASE, 13.0-CURRENT@r344874 amd64 + i386) with options FULL/SUBSET and FULL/HW each -> OK
• portlint -> OK
• Runtime tests by using deskutils/gucharmap -> OK

Minor changes from the original patch:

• Simplify the usage of the options and thus omit the bsd.port.options.mk include
• Removed variables FONTTYPE and FONTFORMAT (I haven't found any occurences of those variables in the ports framework)
• Implicit introducion of variable SRCFONTSDIR that is used by the options