Patch from Pascal Stumpf <Pascal.Stumpf@cubes.de>
The official POSIX name for this signal is SIGCHLD. Linux probably
has SIGCLD only for SysV compatibility, but BSD does not.
In order for this to work, dtsession must be setuid root. If
dtsession is not setuid root, then locking will be disabled, and a
message will be written to ~/.dt/errorlog with the message: "Unable to
lock display due to security restrictions".
Added proper SharedDtSvcReqs in lnxLib.tmpl and CplusplusLibC in
linux.cf. This allows the libstdc++ dependancy to be properly
declared for libDtSvc so that it is not neccessary to hardcode 'CCLINK
= g++' in the Imakefiles of programs linking angainst libDtSvc.