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

*/gen_links: remove TCCOpenSecurity_Functions.hh

The file TCCOpenSecurity_Functions.hh does not exist in a fresh clone of
titan.Libraries.TCCUsefulFunctions. Currently it only gets created after
gen_links.sh ran, created the symlink (to the not yet existing file) and
then ttcn3_compiler writes to it. Adjust the gen_links files to not
create this broken symlink.

Related: https://gitlab.eclipse.org/eclipse/titan/titan.Libraries.TCCUsefulFunctions/-/tree/master/src
Change-Id: Idab86fa1deb0256737167767ee7f5f2b36018df4