Change handling of type conversions for field references
in anonymous structs.
Such types needed to be handled specially,
because the type from Eclipse CDT has no name (anonymous struct),
but our type has a name (we assigned a name to the struct).

However, for some time we did not use the Eclipse CDT type in this
situation anyway, so we do not need the special handling anymore.
Furthermore, the special handling did not support direct access
to members of nested structs.

This fixes #172.

git-svn-id: https://svn.sosy-lab.org/software/cpachecker/trunk@13836 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c