Add pkg-config file for reverse dependencies of BamTools

[SoapZA]

• pkg-config is the de facto standard tool to discover header locations and linker flags, instead of having to guess them.
• The .pc file is API versioned, in order to make it forward compatible with future versions of bamtools that break the API. The allows for a parallel installation of two otherwise incompatible bamtools libraries. See also: https://tecnocode.co.uk/2014/12/09/a-checklist-for-writing-pkg-config-files/ https://developer.gnome.org/programming-guidelines/stable/parallel-installability.html.en