每天进步一点

当前已经itk最新版已经是4.7了，但是项目需要，这里的步骤是成功安装3.20.1。编译环境：Ubuntu 12.04，gcc-4.6

实践证明InsightToolkit-3.20.1.tar.gz在Ubuntu 12.04，64bit，gcc 4.8/gcc 4.7版本上编译都会报同一个错误“‘memcpy’ was not declared in this scope, and no declarations were found by argument-dependent lookup at the point of instantiation [-fpermissive]”。解决方法是：降级为gcc 4.6版本，100%完成通过。