Merge branch 'vr/use-our-perl-in-tests'

Some implementations of Perl terminates "lines" with CRLF even when the script is operating on just a sequence of bytes. Make sure to use "$PERL_PATH", the version of Perl the user told Git to use, in our tests to avoid unnecessary breakages in tests. * vr/use-our-perl-in-tests: t/README: add a bit more Don'ts tests: enclose $PERL_PATH in double quotes t/test-lib.sh: export PERL_PATH for use in scripts t: Replace 'perl' by $PERL_PATH