Merge #161568: boost178: init at 1.78.0

This was merged to `staging` already, but that's just unnecessary delay
after the PR was amended not to change boost defaults.

pkgs/development/libraries/boost/1.78.nix

@@ -0,0 +1,15 @@
+{ callPackage, fetchurl, fetchpatch, ... } @ args:
+
+callPackage ./generic.nix (args // rec {
+  version = "1.78.0";
+
+  src = fetchurl {
+    urls = [
+      "mirror://sourceforge/boost/boost_${builtins.replaceStrings ["."] ["_"] version}.tar.bz2"
+      "https://dl.bintray.com/boostorg/release/${version}/source/boost_${builtins.replaceStrings ["."] ["_"] version}.tar.bz2"
+    ];
+    # SHA256 from http://www.boost.org/users/history/version_1_78_0.html
+    sha256 = "8681f175d4bdb26c52222665793eef08490d7758529330f98d3b29dd0735bccc";
+  };
+})
+

pkgs/development/libraries/boost/default.nix

@@ -45,4 +45,5 @@ in {
   boost174 = makeBoost ./1.74.nix;
   boost175 = makeBoost ./1.75.nix;
   boost177 = makeBoost ./1.77.nix;
+  boost178 = makeBoost ./1.78.nix;
 }

pkgs/top-level/all-packages.nix

@@ -16280,6 +16280,7 @@ with pkgs;
     boost174
     boost175
     boost177
+    boost178
   ;
 
   boost15x = boost159;