Mac OS X doesn't support uname -o. Use uname instead.

I break compatibility with Mac OS X again, that I don't have access
to. Result: Stuff break, and I have to fix it, so it will perhaps
work. At least, I hope it will work.

share/functions/__fish_pwd.fish

@@ -1,8 +1,9 @@
-if test (uname -o) = Cygwin
+switch (uname)
+case 'CYGWIN_*'
 	function __fish_pwd --description "Show current path"
 		pwd | sed -e 's-^/cygdrive/\(.\)/\?-\u\1:/-'
 	end
-else
+case '*'
 	function __fish_pwd --description "Show current path"
 		pwd
 	end

share/functions/hostname.fish

@@ -1,5 +1,7 @@
 # Query for USERDOMAIN to shorten waiting times when OS isn't Windows.
-if set -q USERDOMAIN; and test (uname -o) = Cygwin
+set -q USERDOMAIN
+and switch (uname)
+case 'CYGWIN_*'
 	# Cygwin's hostname is broken when computer name contains Unicode
 	# characters. This hack "fixes" hostname in Cygwin.
 	function hostname --description "Show or set the system's host name"

share/functions/prompt_pwd.fish

@@ -1,12 +1,13 @@
-if test (uname) = Darwin
+switch (uname)
+case Darwin
 	function prompt_pwd --description "Print the current working directory, shortend to fit the prompt"
 		echo $PWD | sed -e "s|^$HOME|~|" -e 's|^/private||' -e 's-\([^/.]\)[^/]*/-\1/-g'
 	end
-else if test (uname -o) = Cygwin
+case 'CYGWIN_*'
 	function prompt_pwd --description "Print the current working directory, shortend to fit the prompt"
 		echo $PWD | sed -e "s|^$HOME|~|" -e 's|^/cygdrive/\(.\)|\1/:|' -e 's-\([^/.]\)[^/]*/-\1/-g' -e 's-^\([^/]\)/:/\?-\u\1:/-'
 	end
-else
+case '*'
 	function prompt_pwd --description "Print the current working directory, shortend to fit the prompt"
 		echo $PWD | sed -e "s|^$HOME|~|" -e 's-\([^/.]\)[^/]*/-\1/-g'
 	end