php54: add pcntl option
pythonPackages.sympy: add expression
nixos-rebuild build-vm: Ignore the user's LUKS devices
linux: Update to 3.2.52
grsecurity: Update to 2.9.1-3.2.52-201310271550
Add option type "str" for unique strings

An annoying and dangerous property of "types.string" is that it merges
multiple definitions by concatenating them, which almost never
produces a sensible result.  (Those options for which it does make
sense typically should use "types.lines" instead, and things only work
because the option definitions already end in a newline.)  Of course,
you can use "types.uniq types.string", but that's rather verbose, and
inconsistent with other basic types like "types.int".

Changing the behaviour of "types.string" to be unique by default is
not an option, given the large number of options that use it.  So
instead, we now have "types.str", which is equivalent to "types.uniq
types.string".
Give types to the Apache httpd options
Support module keys that are paths
Add fixMergeModules back in

NixOps uses it.
fixMergeModules shouldn't check whether options are declared
vimPlugins.ipython: add expression

close #1141
nixos: haproxy module
Manual: Render null values
Fix environment.checkConfigurationOptions

This requires delaying the declaredness check until later, otherwise
we get an infinite recursion querying
environment.checkConfigurationOptions.
changes in: redshift, geoclue, libsoup

 - added support for geoclue for redshift
 - package geoclue 2.0.0 (as geoclue2)
 - package libsoup 2.44.1 (as libsoup_2_40)
Manual: Don't show "Default: none"
Manual: Render strings containing special characters as indented strings
Manual: Escape $
Manual: Render multi-line strings properly
Remove the dhclient module

It's no longer used by NixOS (replaced by dhcpcd).