[gmpfield.hh]

Remove cast operator that caused Clang warnings.
This fixes FS#1207.

Kudos to Ansgar Burchardt for the patch.

[[Imported from SVN: r7064]]

COPYING

@@ -2,7 +2,7 @@ Copyright holders:
 
 2003--2010    Peter Bastian
 2004--2012    Markus Blatt
-2011          Ansgar Burchardt
+2011--2012    Ansgar Burchardt
 2004--2005    Adrian Burri
 2006--2012    Andreas Dedner
 2003          Marc Droske

dune/common/gmpfield.hh

@@ -50,11 +50,6 @@ namespace Dune
     {
       return this->get_d();
     }
-
-    operator mpf_class () const
-    {
-      return static_cast<const mpf_class&>(*this);
-    }
   };