treewide: use https for nixos.org and hydra.nixos.org

tarballs.nixos.org is omitted from the change because urls from there
are always hashed and checked

doc/contributing/quick-start.xml

@@ -111,7 +111,7 @@
     </para>
     <para>
      The exact syntax and semantics of the Nix expression language, including the built-in function, are described in the Nix manual in the <link
-    xlink:href="http://hydra.nixos.org/job/nix/trunk/tarball/latest/download-by-type/doc/manual/#chap-writing-nix-expressions">chapter on writing Nix expressions</link>.
+    xlink:href="https://hydra.nixos.org/job/nix/trunk/tarball/latest/download-by-type/doc/manual/#chap-writing-nix-expressions">chapter on writing Nix expressions</link>.
     </para>
    </listitem>
    <listitem>

doc/languages-frameworks/android.section.md

@@ -167,7 +167,7 @@ parameters that the SDK composition function (the function shown in the
 previous section) supports.
 
 This build function is particularly useful when it is desired to use
-[Hydra](http://nixos.org/hydra): the Nix-based continuous integration solution
+[Hydra](https://nixos.org/hydra): the Nix-based continuous integration solution
 to build Android apps. An Android APK gets exposed as a build product and can be
 installed on any Android device with a web browser by navigating to the build
 result page.

doc/languages-frameworks/ios.section.md

@@ -18,7 +18,7 @@ The primary objective of this project is to use the Nix expression language to
 specify how iOS apps can be built from source code, and to automatically spawn
 iOS simulator instances for testing.
 
-This component also makes it possible to use [Hydra](http://nixos.org/hydra),
+This component also makes it possible to use [Hydra](https://nixos.org/hydra),
 the Nix-based continuous integration server to regularly build iOS apps and to
 do wireless ad-hoc installations of enterprise IPAs on iOS devices through
 Hydra.

doc/preface.chapter.md

@@ -42,7 +42,7 @@ distributed as soon as all tests for that channel pass, e.g.
 [this table](https://hydra.nixos.org/job/nixpkgs/trunk/unstable#tabs-constituents)
 shows the status of tests for the `nixpkgs` channel.
 
-The tests are conducted by a cluster called [Hydra](http://nixos.org/hydra/),
+The tests are conducted by a cluster called [Hydra](https://nixos.org/hydra/),
 which also builds binary packages from the Nix expressions in Nixpkgs for
 `x86_64-linux`, `i686-linux` and `x86_64-darwin`.
 The binaries are made available via a [binary cache](https://cache.nixos.org).

doc/release-notes.xml

@@ -286,7 +286,7 @@ export NIX_MIRRORS_sourceforge=http://osdn.dl.sourceforge.net/sourceforge/</prog
   <note>
    <para>
     This release of Nixpkgs requires <link
-xlink:href='http://nixos.org/releases/nix/nix-0.10/'>Nix 0.10</link> or higher.
+xlink:href='https://nixos.org/releases/nix/nix-0.10/'>Nix 0.10</link> or higher.
    </para>
   </note>
 
@@ -436,7 +436,7 @@ stdenv.mkDerivation {
    <listitem>
     <para>
      Distribution files have been moved to <link
-  xlink:href="http://nixos.org/" />.
+  xlink:href="https://nixos.org/" />.
     </para>
    </listitem>
    <listitem>