Patch taken from the Sage packaging system.

--- src/include/Lcommon.h	2010-01-31 15:16:45.000000000 +0000
+++ src/include/Lcommon.h	2011-03-08 21:19:11.849443238 +0000
@@ -25,7 +25,7 @@
 #ifdef USE_MPFR
 inline double lcalc_to_double(const double& x) { return x; }
 #endif
-//inline double lcalc_to_double(const long double& x) { return x; }
+inline double lcalc_to_double(const long double& x) { return x; }
 inline double lcalc_to_double(const int& x) { return x; }
 inline double lcalc_to_double(const long long& x) { return x; }
 inline double lcalc_to_double(const short& x) { return x; }
