lib: speed up slow parts of the lib files; other small fixes

lib/functions.zsh

@@ -89,7 +89,7 @@ function default() {
 #    0 if the env variable exists, 3 if it was set
 #
 function env_default() {
-    (( ${${(@f):-$(typeset +xg)}[(I)$1]} )) && return 0
+    [[ ${parameters[$1]} = *-export* ]] && return 0
     export "$1=$2" && return 3
 }