build: make install in "/doc" failed if the destination dir contained spaces
This and the following commits try to add the necessary quoting in the build
scripts to make the process more robust.
The target for now is rendering "make deb" successful even when the base
directory contains spaces (eg. "/opt/mercu rial").
The build process should succeed without scattering files in spurious
directories (eg.: "/opt/mercu/usr/bin/hg").
To run the tests, do:
cd tests/
python run-tests.py
See https://mercurial-scm.org/wiki/WritingTests for
more information on writing tests.