converters/cbmconvert: update to 2.1.4.

This is a maintenance release of cbmconvert after a 15-year break. Some old
source code releases were imported as snapshots, because no version control
system had been used in the past.

What's Changed

-  Empty files are now supported.
-  The build system was converted to CMake.
-  Some test cases with CTest were introduced.
-  Support for CPack packaging as well as native Debian packages was
    implemented.

Full Changelog: https://github.com/dr-m/cbmconvert/commits/cbmconvert-2.1.4

(rhialto)