jpeg plugin crashes in Win64

[nicolas-cellier-aka-nice]

My 1st finding is that crashes allways occur in setjump().

setjump() is used in primJPEGWriteImageonByteArrayformqualityprogressiveJPEGerrorMgrWriteScanlines as the return point for the error_exit() - called by jpeg library in case of error.
See platforms/Cross/plugins/JPEGReadWriter2Plugin/sqJPEGReadWriter2Plugin.c

error_exit() will then use longjmp to go to the exit point.
See platforms/Cross/plugins/JPEGReadWriter2Plugin/Error.c

But the call to setjump does not allways crash. It sometimes succeed, sometimes crash.

My 2nd finding is that it works when the jump_buf is 16-bytes aligned (hex address ending by 0), but fails when 8 bytes-aligned (hex address ending by 8).

This seems confirmed by other bug reports (google: setjmp win64 failure 16bytes aligned)
https://bugs.launchpad.net/pbxt/+bug/688404

A workaround would be to store a pointer to the jump_buf in struct error_mgr2, and properly align the jump_buf with alloca() or something...

[nicolas-cellier-aka-nice]

Fixed by pull request #120, commit 9ffa643