occurrences of "/" in the argument list. This corresponds to Enhancement
Request Number 5 in the Austin Group TC2 Aardvark's XCU Defects Report
(<URL:http://www.opengroup.org/austin/aardvark/finaltext/xcubug.txt>).
Further discussion is available in the Austin Group mailing list archives
(<URL:http://www.opengroup.org/austin/mailarchives/>, "Defect in XCU rm")
and for Austin Group members, in the Austin Group Interpretations archive
(<URL:http://www.opengroup.org/austin/interps/>, AI-019)
This commit makes that check conditional on !POSIXLY_CORRECT, since it
is not strictly correct according to the current version of the standard
(but is expected to be correct according to the next version, and has
already been adopted by Solaris).