Pkgsrc port of yasr

[adr-adr]

Hi, I've created a pkgsrc port of yasr. These are mostly all the changes I made:

• Add header tests in meson.build.
• Remove non-portable use of WCHAR_T in iconv code.
• Remove the enforcing of UTF-8.
• Fix the reading of char after space using right cursor key.
• Use defined constants in buffer sizes when they are used elsewhere.
• Remove unused argument of gulp().
• Fix bug: buf[] used instead of kbuf[].
• Fix bug: the reading of master can be truncated even just getting one char at
  a time (bug in NetBSD's pty implementation?), the code has to take that into account.
• Simplify formatting now that we are there, but according to the rest of the code.

patch-meson.build.patch
patch-yasr_main.c.patch
patch-yasr_tts.c.patch
patch-yasr_yasr.h.patch