libcdecl: Fix spacing after pointer qualifiers (again).

Some renderings of pointer qualifiers have an unwanted trailing space,
for example:

  > type const pointer to array of int
  int (* const )[]

This exact bug was fixed before, more than 10 years ago, but as no test
case was added it took some time to notice the problem when the fix was
inadvertently deleted.  This time, we fix it again, and also add some
test cases to verify the output.