Merge 'staging' into closure-size

- there were many easy merge conflicts
- cc-wrapper needed nontrivial changes

Many other problems might've been created by interaction of the branches,
but stdenv and a few other packages build fine now.

pkgs/development/libraries/mpfr/default.nix

@@ -10,7 +10,11 @@ stdenv.mkDerivation rec {
 
   outputs = [ "dev" "out" "doc" ];
 
-  buildInputs = [ gmp ];
+  # mpfr.h requires gmp.h
+  propagatedBuildInputs = [ gmp ];
+
+  CFLAGS = "-I${gmp}/include";
+  LDFLAGS = if stdenv.isDarwin then "-L${gmp}/lib" else null;
 
   configureFlags =
     /* Work around a FreeBSD bug that otherwise leads to segfaults in the test suite:
@@ -43,7 +47,7 @@ stdenv.mkDerivation rec {
 
     license = stdenv.lib.licenses.lgpl2Plus;
 
-    maintainers = [ stdenv.lib.maintainers.ludo ];
+    maintainers = [ ];
     platforms = stdenv.lib.platforms.all;
   };
 }