The man page states
  Values are separated from directives by whitespace and/or an
  optional =.

But logrotate does accept no separator, like
  rotate7

Log those occurrences with a normal severity, as this usage is not
intended.

isolateWord() only fails on OOM and EOF.

Consider the following configuration:
    olddir /var/log/foo
    noolddir

Do not leak the memory of the initial olddir path.

Allow a tab in between the option keyword and its value, like
    dateformat\t.%Y%m%d

Currently the tab would be included in the format string, leading to
tabs in rotated files.

Also drop unnecessary continue block, since this is the default next
action.

Reiterating the loop is the default next action.

Fail on a parse error of a required option value of the directives
include, extension, addextension, rotate, start, minage, maxage,
shredcycles and su.
Failing is better than silently skipping a directive and running with an
undesired configuration.

Make it more visible.
No one sees debug logs if nothing fails.

Increase severity from debug to normal in case the configuration has a
potential dangerous file mode; make it more visible.
No one sees debug logs if nothing fails.