Do not install headers from external libraries
Description
Do not install header files from external libraries.
Fixes #107 (closed) #124 (closed).
News snippet
Fixed incorrect installation of header files from libyaml and spglib external libraries.
Checklist
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I have checked that my code follows the Octopus coding standards -
I have added tests for all the new features added in this request.
Edited by Micael Oliveira