Get ready for deprecating this repository

[bassosimone]

This repository used to be used by most mk* sub-libraries. Now most sub-libraries have been converted to using measurement-kit/mkbuild instead. Remaining libs:

• github.com/measurement-kit/mkorchestra (see measurement-kit/mkorchestra#6)

• github.com/measurement-kit/libndt (see measurement-kit/libndt#91)

• github.com/measurement-kit/mkudns (see measurement-kit/mkudns#1)

When they will be converted, we can mark this repository as deprecated and freeze it.

[bassosimone]

Libdnt has not been converted yet. I already have code in measurement-kit/libndt#108 for replacing cmake-modules. At this point it's fair to archive this repository, considering that there will be no further updates of the code.