Possible mismatch about LIBXC PACKAGE installation in Makefile  #5

Hi,

Thanks for sharing this helpful software.
Just a reminder: While compiling your code step by step following the instructions in Makefile, I found that there may exist a mismatch in the note for LIBXC PACKAGE INSTALLATION. Detailedly, I was told PROFESS 3 depends on Libxc library (2.0.1 version is tested), Important note: the interfaces change since the new version Libxc 2.1.0, so please use version before that. However, all versions from Libxc 2.0.1 to 2.1.0 didn't work well in my Unix environment. And I find the suitable version (3.0.0) from the replicated repo of one of the authors.