This fixes the verification in validateSpec()

SAFE_FREE has set defaultUnixPath_ to NULL already

==7689== 50 bytes in 5 blocks are definitely lost in loss record 1 of 2
==7689==    at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==7689==    by 0x54074D9: strndup (strndup.c:43)
==7689==    by 0x4E7D803: ChannelEndPoint::getTCPHostAndPort(char**, long*) const (ChannelEndPoint.cpp:309)
==7689==    by 0x4EC9D93: ConnectToRemote(ChannelEndPoint&) [clone .constprop.144] (Loop.cpp:6660)
==7689==    by 0x4ECB94E: SetupProxyConnection() (Loop.cpp:3204)
==7689==    by 0x4ECE824: handleNegotiationInLoop(int&, fd_set&, fd_set&, timeval&) [clone .isra.129] (Loop.cpp:14312)
==7689==    by 0x4ED0F8A: NXTransPrepare (Loop.cpp:2575)
==7689==    by 0x4ED1C35: NXTransContinue (Loop.cpp:1609)
==7689==    by 0x4ED1D7B: WaitCleanup() (Loop.cpp:4440)
==7689==    by 0x4ED2343: NXTransProxy (Loop.cpp:1234)
==7689==    by 0x400B2A: main (Main.c:111)

Should be used instead of free() calls and will clear the pointer after
calling free(). This can prevent double-free or use-after-free errors.

free() can handle NULL itself

Fixes ArcticaProject/nx-libs#569

Commit 5f1eb0dc introduced a regression
that made the use of the multimedia port mandatory.

Fixes ArcticaProject/nx-libs#525

This makes it so that slave=1 works again as it should.

The changes introduced earlier resulted in the unintentional requirement
to specify the actual port number, breaking backwards compatibility.

Fixes: ArcticaProject/nx-libs#518

Fixes: ArcticaProject/nxlibs#389.

Per-file copyright notices: Update copyright information in file headers that NoMachine placed there own copyright statement in.