in the system-wide version of <stdlib.h> by wrapping the #include_next
<stdlib.h> within the scope of its own header protection. On FreeBSD this has
no effect, since both header protections are equivalent. However the GNU version
of <stdlib.h> implements a special header protection mechanism which allows it
to be included multiple times (in different modes).
Simply by moving the #include_next off the header protection, we allow
system-wide <stdlib.h> to implement its own protection policy, whichever that
may be.
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