Circular dependencies in subsurface

[Patrick Valsecchi]

Dirk,

You introduced weird circular dependencies with you commit 5bf86f6042 
that makes fixing the CMakeLists.txt impossible.

Now qthelper.cpp (in subsurface_corelib) needs UserSurvey which is 
provided by subsurface_interface which in turn needs subsurface_corelib.

I don't know how we can fix that... either move reverseGeoLookup 
somewhere else (tough since parse-xml.c is using it) or remove the split 
in different libs in the CMakeLists.txt (should be OK, but I don't know 
why we had it in a first place).

CU