This issue was introduced in 5557fd22173ea9ab4c02c81e1dcec9bd6927814f
due to an oversight, so it has existed in libjpeg-turbo since the
project's inception.  However, the issue is effectively a non-issue.
Although #325 proposes allowing programs to override jpeg_get_*() and
jpeg_free_*() externally, there is currently no way to override those
functions without modifying the libjpeg-turbo source code.
libjpeg-turbo only includes the malloc()/free() memory manager from
libjpeg, and the implementation of jpeg_free_*() in that memory manager
ignores the size argument.  libjpeg had several additional memory
managers for legacy systems (MS-DOS, System 7, etc.), but those memory
managers ignored the size argument to jpeg_free_*() as well.  Thus, this
issue would have only potentially affected custom memory managers in
downstream libjpeg-turbo forks, and since no one has complained until
now, apparently those are rare.

Fixes #542