debian: add less as a build dependency
For builds that run on hermetic environments, it's possible that the "less"
package is not installed by default, yet it's needed for tests to pass after
revision bf5e13e38390 (which sets less as the fallback pager).
Mercurial
=========
Mercurial is a fast, easy to use, distributed revision control tool
for software developers.
Basic install:
$ make # see install targets
$ make install # do a system-wide install
$ hg debuginstall # sanity-check setup
$ hg # see help
Running without installing:
$ make local # build for inplace usage
$ ./hg --version # should show the latest version
See https://mercurial-scm.org/ for detailed installation
instructions, platform-specific notes, and Mercurial user information.