title: "Symbol from plugin" in linker error
body: <p>So, I did something dumb and got myself a linker error:</p>
  
  <pre><code>CMakeFiles/pipeline.dir/src/pipeline/pipelineElements/tracker/ObjectTracker.cpp.o (symbol from plugin): In function `ObjectTracker::process(long)':
  (.text+0x0): multiple definition of `BackgroundSubtract::OptionTypes&lt;(BackgroundSubtractOptionID)0&gt;::type PipelineConfiguration::getOption&lt;BackgroundSubtract, (BackgroundSubtractOptionID)0&gt;(BackgroundSubtract const&amp;) const'
  CMakeFiles/pipeline.dir/src/pipeline/pipelineElements/RegionFinder.cpp.o (symbol from plugin):(.text+0x0): first defined here
  CMakeFiles/pipeline.dir/src/pipeline/pipelineElements/tracker/ObjectTracker.cpp.o (symbol from plugin): In function `ObjectTracker::process(long)':
  </code></pre>
  
  <p>I'm curious about what the "symbol from plugin" part means? I've never seen that before in my various adventures with linker errors. What's a "plugin" in this context?</p>