On Ubuntu 11.10 the host library created for the 'lx_hybrid_ctors' test
doesn't get loaded, because the test object in the library is not being
used by the application. This commit fixes the problem by having the
application call a dummy function in the library.
Fixes#120.
- Let hybrid Linux/Genode programs use POSIX threads for the
implementation of the Thread API.
- Prevent linkage of cxx library to hybrid Linux/Genode programs because
the cxx functionality is covered by glibc.