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/development/libraries/libmpc/default.nix

@@ -0,0 +1,34 @@
+{ fetchurl, stdenv, gmp, mpfr }:
+let
+  version = "1.0.1";
+in
+stdenv.mkDerivation rec {
+  name = "libmpc-${version}"; # to avoid clash with the MPD client
+
+  src = fetchurl {
+    url = "http://www.multiprecision.org/mpc/download/mpc-${version}.tar.gz";
+    sha1 = "vxg0rkyn4cs40wr2cp6bbcyr1nnijzlc";
+  };
+
+  buildInputs = [ gmp mpfr ];
+
+  CFLAGS = "-I${gmp}/include";
+
+  doCheck = true;
+
+  meta = {
+    description = "Library for multiprecision complex arithmetic with exact rounding";
+
+    longDescription =
+      '' GNU MPC is a C library for the arithmetic of complex numbers with
+         arbitrarily high precision and correct rounding of the result.  It is
+         built upon and follows the same principles as GNU MPFR.
+      '';
+
+    homepage = http://mpc.multiprecision.org/;
+    license = stdenv.lib.licenses.lgpl2Plus;
+
+    platforms = stdenv.lib.platforms.all;
+    maintainers = [ ];
+  };
+}