Decouple command/OtherCommands.cxx from the "simple" database plugin.

Don't depend on the "simple" database plugin.  This fixes an assertion
failure / crash and allows using stickers with other plugins.

Make it "const".

sed gone horribly wrong.  D'oh!

pthread_setname_np() doesn't have the "thread" argument on OS X.

Fixes non-Linux build without neighbor plugins.

Another big chunk of code for multi-player support.

The pkg-config file has been added in Samba 4.0.  This commits adds a
fallback for older libsmbclient versions.

Allow semicolons and single quotes in the stream title.  This is not
part of any specification, but found in real life.

We're C++, and sparse understands only plain C.

Was broken on out-of-tree builds.

This was just too complex and fragile.  Anybody who has versioned
program names shall just call those programs manually.

I expect that aclocal is clever enough to find its own include
directories.  If it does not, letting MPD guess it is not the most
reliable idea either.

This call was unnecessary.  It is a bad idea anyway to block the MPD
process for some arbitrary amount of time.