remove long double from ctypes value union

It is unused. It also forces a 16-byte alignment, which creates problems because
Python's allocator only uses 8-byte alignment.

Modules/_ctypes/ctypes.h

@@ -34,7 +34,6 @@ union value {
 #ifdef HAVE_LONG_LONG
                 PY_LONG_LONG ll;
 #endif
-                long double D;
 };
 
 /*
@@ -306,7 +305,6 @@ struct tagPyCArgObject {
 #ifdef HAVE_LONG_LONG
         PY_LONG_LONG q;
 #endif
-        long double D;
         double d;
         float f;
         void *p;