zshrc: Fix compatibility with zsh 4

zshrc

@@ -5,7 +5,7 @@ export EDITOR="vim"
 export VIMINIT="source $XDG_CONFIG_HOME/vim/vimrc"
 export PAGER="less"
 export LS_COLORS='di=34:ow=44;37:tw=44;37:st=44;37:ex=31:su=7;31:sg=7;31:ln=33:or=7;33:pi=32:do=32:bd=35:cd=35:so=32:*.bz2=36:*.dmg=36:*.gz=36:*.gpg=36:*.rar=36:*.tar=36:*.tbz2=36:*.tgz=36:*.xz=36:*.zip=36:*.orig=90:*~=90'
-export SUDO_PROMPT=$(printf "\033[0;31m[\033[1;31msudo -> %%U\033[0;31m]\033[0m Password for \033[1m%%p@%%H\033[0m: ")
+export SUDO_PROMPT="$(printf "\033[0;31m[\033[1;31msudo -> %%U\033[0;31m]\033[0m Password for \033[1m%%p@%%H\033[0m: ")"
 export GNUPGHOME="$XDG_DATA_HOME/gnupg"
 export CVS_RSH="ssh"
 LISTMAX=32768
@@ -18,28 +18,34 @@ local ls_on_cd="yes"
 local ls_on_init="no"
 local normal_user="js"
 
-if [ "$COLORTERM" = "24bit" -o "$COLORTERM" = "truecolor" \
+autoload -U is-at-least
+
+if is-at-least 5.0.0 && [ "$COLORTERM" = "24bit" -o "$COLORTERM" = "truecolor" \
     -o "$terminfo[colors]" = 16777216 ]; then
 	local color_cwd="#209060"
 	local color_host="#176945"
 	local color_suffix="#29bc7d"
 	local color_vcs="#43d696"
 	local color_vcs_braces="#29bc7d"
-elif [ "$terminfo[colors]" = 256 ]; then
+	local color_jobs="yellow"
+	local color_status="red"
+elif is-at-least 5.0.0 && [ "$terminfo[colors]" = 256 ]; then
 	local color_cwd="29"
 	local color_host="23"
 	local color_suffix="36"
 	local color_vcs="78"
 	local color_vcs_braces="36"
+	local color_jobs="yellow"
+	local color_status="red"
 else
 	local color_cwd=2
 	local color_host=6
 	local color_suffix=2
 	local color_vcs=2
 	local color_vcs_braces=2
+	local color_jobs=3
+	local color_status=1
 fi
-local color_jobs="yellow"
-local color_status="red"
 
 bindkey -v
 # history-incremental-search-backward is much more useful than
@@ -116,21 +122,31 @@ Apple_Terminal)
 esac
 
 set_prompt() {
+	if is-at-least 5.0.0; then
+		color() { printf "%%F{$1}" }
+		nocolor() { printf "%%f" }
+	else
+		color() { printf "%%{\033[3${1}m%%}" }
+		nocolor() { printf "%%{\033[0m%%}" }
+	fi
+
 	if [ -n "$1" ]; then
-	       	local branch="%F{$color_vcs_braces}(%F{$color_vcs}$1"
+	       	local branch="$(color $color_vcs_braces)($(color $color_vcs)$1"
-		branch+="%F{$color_vcs_braces})"
+		branch+="$(color $color_vcs_braces))"
 	fi
 
 	if [ "$(whoami)" != "$normal_user" ]; then
 		local user="%n@"
 	fi
 
-	PS1="%F{$color_host}$user%m %F{$color_cwd}%c$branch"
+	PS1="$(color $color_host)$user%m $(color $color_cwd)%c$branch"
-	PS1+="%F{$color_suffix}%(!.#.>)%f "
+	PS1+="$(color $color_suffix)%(!.#.>)$(nocolor) "
 	PS2="%B>%b "
-	RPS1="%(1j.%F{$color_jobs}%B%j%b%f.)%(?..%(1j. .)"
+	RPS1="%(1j.$(color $color_jobs)%B%j%b$(nocolor).)%(?..%(1j. .)"
-	RPS1+="%F{$color_status}%B%?%b%f)"
+	RPS1+="$(color $color_status)%B%?%b$(nocolor))"
-	RPS2="%(1_.%F{black}%B(%_%)%b%f.)"
+	RPS2="%(1_.$(color black)%B(%_%)%b$(nocolor).)"
+
+	unfunction color nocolor
 }
 set_prompt
 
@@ -158,7 +174,7 @@ aterm|Eterm|rxvt*|uxterm*|xterm*)
 
 	unset_title() {
 		precmd() {
-			print -Pn "\e]0;%c · %m\a"
+			print -Pn "\e]0;%m:%c\a"
 			__precmd
 		}
 	}
@@ -222,7 +238,9 @@ __has_command vim && alias vi=vim
 __has_command gpg2 && alias gpg=gpg2
 
 if [ "$(uname -s)" = "Darwin" ]; then
-	export MAKEFLAGS="-j$(($(sysctl -n machdep.cpu.thread_count) * 2))"
+	local thread_count="$(sysctl -n machdep.cpu.thread_count 2>/dev/null)"
+	test -z "$thread_count" && thread_count=1
+	export MAKEFLAGS="-j$((thread_count * 2))"
 elif [ "$(uname -s)" = "NetBSD" ]; then
 	export MAKEFLAGS="-j$(($(/sbin/sysctl -n hw.ncpu) * 2))"
 elif __has_command nproc; then