Allow Gnu gcc's to build python on OSX by removing -Wno-long-double,

Allow Gnu gcc's to build python on OSX by removing -Wno-long-double,
-no-cpp-precomp, and -mno-fused-madd from configure.
 * r22183 added -no-cpp-precomp, which
   http://gcc.gnu.org/ml/gcc/2005-12/msg00368.html claims hasn't been
   needed since gcc-3.1.
 * r25607 added -Wno-long-double to avoid a warning in
   Include/objimpl.h (issue 525481). The long double is still there,
   but OSX 10.4's gcc no longer warns about it.
 * r33666 fixed issue 775892 on OSX 10.3 by adding -mno-fused-madd,
   which changed the sign of some float 0s. Tim Peters said it wasn't
   a real issue anyway, and it no longer causes test failures.
Fixes issue #1779871.