规范模块目录和第三方依赖结构

third_party/eigen3/doc/examples/Cwise_erfc.cpp

@@ -0,0 +1,9 @@
+#include <Eigen/Core>
+#include <unsupported/Eigen/SpecialFunctions>
+#include <iostream>
+using namespace Eigen;
+int main()
+{
+  Array4d v(-0.5,2,0,-7);
+  std::cout << v.erfc() << std::endl;
+}