下载protobuf-2.4.1.tar.gz：
http://protobuf.googlecode.com/files/protobuf-2.4.1.tar.gz
安装：
tar zxvf protobuf-2.4.1.tar.gz
cd protobuf-2.4.1
./configure
make
make check
make install
安装结束。
验证：
查看是否安装成功：protoc --version
如果出现：libprotoc 2.4.1 则说明安装成功！
如果出现错误：
protoc: error while loading shared libraries: libprotobuf.so.0: cannot open
shared object file: No such file or directory
The issue is that Ubuntu 8.04 doesn't include /usr/local/lib in
library paths.
 
To fix it for your current terminal session, just type in
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/lib