Changes

*/gen_links.sh: fix wrong SDP_EncDec.cc symlink

SDP_EncDec.cc is not in titan.Libraries.TCCUsefulFunctions, it is in
titan.ProtocolModules.SDP. The gen_links.sh scripts had instructions to
symlink both the wrong and right location of SDP_EncDec.cc, and most of
the time the right location would be symlinked.

When the wrong location was symlinked, the next command
regen_makefile.sh would fail with:

  ttcn3_makefilegen: error: Cannot find any source file for argument `SDP_EncDec.cc'.

Change-Id: I5799ee04b9897fb58a92cf222bcffbf97275d7c1