widl: Print EXPR_NUM expresssions as unsigned to avoid printing an extra negative sign when lval is large.

ole32: The stream returned by StgStreamImpl_Clone should have one reference, so call AddRef before returning.

Move the call to StorageBaseImpl_AddStream to StgStreamImpl_Construct to 
fix StgStreamImpl_Clone, which forgets to call it.
Add tests for OLE structured storage tests for IStream::Clone.

dbghelp: Allow to add an alternate file_map for an ELF file (where to look for its debug information).