fixes problem with command line flags -d and -s
fixes problem with command line flags -d and -s

Command line flags that don’t take options (-d and -s) were ignored if
they were in the last position, since the while loop in plaac.java
stopped at the next-to-last index (though it would grab an option from
the last index). This did not affect server code, since the -d and -s
flags were used only in build_docs.py, where neither was in the last
position.

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