textproc/linux-c7-expat-devel: Add new port

[zirias]

Summary

This contains the headers to build Linux software using expat.
Also add USE_LINUX=expat-devel.

[zirias]

These new ports would enable me to get rid of several dirty hacks in multimedia/makemkv.

[tcberner]

Moin moin

Please run
> git config --add core.hooksPath .hooks
in your ports checkout.

That would warn you on commit that you forgot to add SUBDIR in textproc/Makefile

mfg Tobias

[zirias]

Add missing SUBDIR.

[zirias]

For some more background:

To get MakeMKV to work on FreeBSD, it needs to build a library targeting Linux that's then used by the closed-source makemkvcon binary. This stack of reviews contains three of its four build dependencies. The fourth, ffmpeg, needs to be built in the port and linked statically anyways, because linux-c7 doesn't offer something usable.

For the other ones, I had workarounds so far:

• for zlib and expat, I used FreeBSD headers (from base resp. ports). This worked, but is slightly fragile.
• for openssl, FreeBSD headers are unusable cause they are the wrong version, so the makemkv port had to fetch the original distfile to get usable headers.

So, instead using these new ports improves the quality of multimedia/makemkv and also greatly simplifies it (I'm down to 133 lines in my local branch now, and this is after lots of structure improvements and also adding a new knob to make fdk-aac optional when building ffmpeg).

[zirias]

Rebase and move WWW from pkg-descr to Makefile.