fix ubuntu18.04 unity compile issue

If you are using ubuntu 18.04+, but still using unity desktop, you will find that the original installation of ppa source is also useless, and the download of the source code can not be compiled successfully, prompting the lack of dependent libraries. To solve this problem, I forked the library and made the following changes:

The dependency library libappindicator3-dev was changed to libayatana-appindicator3-dev and the second line of include in the source code was changed to: #include

The dependency appindicator3-0.1 in the Makefile should be changed to ayatana-appindicator3-0.1 and then it will be compiled and installed successfully.

or you can just use my fork repository: https://github.com/wangbjun/indicator-netspeed

Inspect the Makefile dependency entry and the C source include mentioned in the issue. Compare the existing appindicator references with the Ayatana replacements, then verify that the project compiles successfully on Ubuntu 18.04+ using Unity.

Written by the indexing model from the issue text.