shared lib and __data_start

[Ellery Newcomer]

Playing with pypy.

I build me a shared library with ldc and try to access it via ctypes, 
and it gives me a

/usr/lib64/libdruntime-ldc.so.60: undefined symbol: __data_start

So the natural question is what is __data_start? Am I right in assuming 
it is a symbol that points to the data section or something and that it 
is relevant in executables but not shared libraries (and thus shouldn't 
be in druntime for shared lib builds)?