error which arose when one module define a value with "mkDefaultValue"
and another module define its value with "mkIf <false>".
svn path=/nixpkgs/trunk/; revision=17759
- types.nix:
Introduce a new flag named "delayProperties" which define either that
properties should be evaluated (when false) or that they should be delaied
through the type structure.
- properties.nix:
Generalized the delayProperties function to make it work with the iter
functions of option types.
- modules.nix:
Replace evalProperties by a condition based on the value of the
"delayProperties" flag of the option type. If the flag does not exists or
if it is false, then the system behaves as always. Otherwise it delays
the properties from the current value to each values contained inside it.
svn path=/nixpkgs/trunk/; revision=17736
