vim-patch:9.1.1081: has('bsd') is true for GNU/Hurd

Problem:  has('bsd') is true for GNU/Hurd
Solution: exclude GNU/Hurd from BSD feature flag
          (Zhaoming Luo)

GNU/Hurd, like Mac OS X, is a BSD-based system. It should exclude
has('bsd') feature just like what Mac OS X does. The __GNU__ pre-defined
macro indicates it's compiled for GNU/Hurd.

closes: vim/vim#16580

a41dfcd55b

Co-authored-by: Zhaoming Luo <zhmingluo@163.com>

src/nvim/eval.lua

@@ -5119,6 +5119,7 @@ M.funcs = {
       	fname_case	Case in file names matters (for Darwin and MS-Windows
       			this is not present).
       	gui_running	Nvim has a GUI.
+      	hurd		GNU/Hurd system.
       	iconv		Can use |iconv()| for conversion.
       	linux		Linux system.
       	mac		MacOS system.