Fix ls command under Cygwin

It appears that dircolors -c under Cygwin has >&/dev/null at end that is
valid C shell syntax, but isn't accepted in fish shell.
Fix hostname command under Cygwin with Unicode characters

Yes, hostname is broken under Cygwin, but for fish it's an issue, as it
makes fish_config more buggy than it needs to be (by making UTF-8 errors
according to Python).
Ignore executable files

I commited executables in previous commit (removed using git push
--force - sorry, I wouldn't want to waste space in git repository), so I
think *.exe files should be forbidden to avoid any problems (there is no
reason to ever commit them)
Merge remote-tracking branch 'upstream/master'