Merge 'mingw-w64' and 'darwin' into cross-win-osx.

Both branches have quite a lot in common, so it's time for a merge and
do the cleanups with respect to both implementations and also generalize
both implementations as much as possible.

This also closes #1876.

Conflicts:
	pkgs/development/interpreters/lua-5/5.2.nix
	pkgs/development/libraries/SDL/default.nix
	pkgs/development/libraries/glew/default.nix
	pkgs/top-level/all-packages.nix

pkgs/development/interpreters/lua-5/5.2.nix

@@ -17,7 +17,7 @@ stdenv.mkDerivation rec {
     sha256 = "004zyh9p3lpvbwhyhlmrw6wwcia5abx84q4h2brkn4zdypipvmiz";
   };
 
-  buildInputs = [ readline ];
+  nativeBuildInputs = [ readline ];
 
   patches = [ dsoPatch ];
 
@@ -49,6 +49,37 @@ stdenv.mkDerivation rec {
     EOF
   '';
 
+  crossAttrs = let
+    isMingw = stdenv.cross.libc == "msvcrt";
+    isDarwin = stdenv.cross.libc == "libSystem";
+  in {
+    configurePhase = ''
+      makeFlagsArray=(
+        INSTALL_TOP=$out
+        INSTALL_MAN=$out/share/man/man1
+        CC=${stdenv.cross.config}-gcc
+        STRIP=:
+        RANLIB=${stdenv.cross.config}-ranlib
+        V=${majorVersion}
+        R=${version}
+        ${if isMingw then "mingw" else stdenv.lib.optionalString isDarwin ''
+        AR="${stdenv.cross.config}-ar rcu"
+        macosx
+        ''}
+      )
+    '' + stdenv.lib.optionalString isMingw ''
+      installFlagsArray=(
+        TO_BIN="lua.exe luac.exe"
+        TO_LIB="liblua.a lua52.dll"
+        INSTALL_DATA="cp -d"
+      )
+    '';
+  } // stdenv.lib.optionalAttrs isDarwin {
+    postPatch = ''
+      sed -i -e 's/-Wl,-soname[^ ]* *//' src/Makefile
+    '';
+  };
+
   meta = {
     homepage = "http://www.lua.org";
     description = "Powerful, fast, lightweight, embeddable scripting language";