- use `Requires.private` in pkgconfig files to stop forcing downstream
  packages to link against everything upstream
- added `pkgconfig` as `BuildRequires` for RPMs
- bumped required version of pkg-config to 0.18.0

- gstlal_compute_strain:  numerous small bug fixes to get kappa_U calculation to work with new channels.
- tests/check_calibration:  Added plotting for GDS / CALCS transfer function.  Still needs dewhitening.
- debian/gstlal-calibration.install:  edits to make gstlal-calibration build on Debian

gstlal-calibration-1.2.3 release.  Includes a minor bug fix so that all needed plugins get built and packaged.

gstlal-calibration:  Update gstlal-calibration.spec.in and debian/gstlal-calibration.install to package everything we need.

Update to Debian build from Steffen's patch and bug fix in gstlal_smoothkappas.c for misplaced parentheses