Fix minimal/do and tests when built in a path containing spaces.

Basically all just missing quotes around shell strings that use $PWD.
Most paths inside a project, since redo uses relative paths, only need
to worry when project-internal directories or filenames have spaces in
them.

Reported-by: Jeff Stearns <jeff.stearns@gmail.com>

t/360-symlinks/a.do

@@ -2,6 +2,6 @@ printf x >>a.ran
 rm -f dir/$2.1 $2.2 $2.3 $2.final
 echo foo >$2.final
 ln -s $2.final $2.3
-ln -s $PWD/$2.3 $2.2
+ln -s "$PWD/$2.3" $2.2
 ln -s ../$2.2 dir/$2.1
 ln -s dir/$2.1 $3