Big 1213: add regression unit test.

test/bug1213_main.cpp

@@ -0,0 +1,18 @@
+
+// This is a regression unit regarding a weird linking issue with gcc.
+
+#include "bug1213.h"
+
+int main()
+{
+  return 0;
+}
+
+
+template<typename T, int dim>
+bool bug1213_2(const Eigen::Matrix<T,dim,1>& )
+{
+  return true;
+}
+
+template bool bug1213_2<float,3>(const Eigen::Vector3f&);