mpc: also rename the attribute to libmpc

Attrnames and package names should be as close as possible to avoid confusion.
I took care not to confuse the two mpc things during the mass-replace,
so hopefully I suceeded (tarball still builds).

pkgs/stdenv/linux/default.nix

@@ -207,7 +207,7 @@ rec {
       # reduces the size of the stdenv closure.
       gmp = pkgs.gmp.override { stdenv = pkgs.makeStaticLibraries pkgs.stdenv; };
       mpfr = pkgs.mpfr.override { stdenv = pkgs.makeStaticLibraries pkgs.stdenv; };
-      mpc = pkgs.mpc.override { stdenv = pkgs.makeStaticLibraries pkgs.stdenv; };
+      libmpc = pkgs.libmpc.override { stdenv = pkgs.makeStaticLibraries pkgs.stdenv; };
       isl = pkgs.isl.override { stdenv = pkgs.makeStaticLibraries pkgs.stdenv; };
       cloog = pkgs.cloog.override { stdenv = pkgs.makeStaticLibraries pkgs.stdenv; };
       gccPlain = pkgs.gcc.cc;

pkgs/stdenv/linux/make-bootstrap-tools-crosspi.nix

@@ -81,7 +81,7 @@ let
   cloog = pkgs.cloog.crossDrv;
   zlib = pkgs.zlib.crossDrv;
   isl = pkgs.isl.crossDrv;
-  mpc = pkgs.mpc.crossDrv;
+  libmpc = pkgs.libmpc.crossDrv;
   binutils = pkgs.binutils.crossDrv;
   klibc = pkgs.linuxPackages.klibc.crossDrv;
 
@@ -188,7 +188,7 @@ rec {
         cp -d ${cloog}/lib/libcloog*.so* $out/lib
         cp -d ${ppl}/lib/libppl*.so* $out/lib
         cp -d ${isl}/lib/libisl*.so* $out/lib
-        cp -d ${mpc}/lib/libmpc*.so* $out/lib
+        cp -d ${libmpc}/lib/libmpc*.so* $out/lib
         cp -d ${zlib}/lib/libz.so* $out/lib
         
         # Copy binutils.

pkgs/stdenv/linux/make-bootstrap-tools.nix

@@ -113,7 +113,7 @@ rec {
 
         cp -d ${gmpxx}/lib/libgmp*.so* $out/lib
         cp -d ${mpfr}/lib/libmpfr*.so* $out/lib
-        cp -d ${mpc}/lib/libmpc*.so* $out/lib
+        cp -d ${libmpc}/lib/libmpc*.so* $out/lib
         cp -d ${zlib}/lib/libz.so* $out/lib
         cp -d ${libelf}/lib/libelf.so* $out/lib