Fix #77195: Incorrect error handling of imagecreatefromjpeg()

Fix #77195: Incorrect error handling of imagecreatefromjpeg()

The broken JPEG image triggers a notice, two warnings and outputs a
message to stderr directly.  The additional notice is pretty useless,
and the direct output to stderr is bad.  Therefore, we port the
relevant differences from upstream to our bundled libgd.  This leaves
us with two warnings; the first one is triggered by libjpeg and shows
the actual problem, the second one is triggered by our libgd wrapper
whenever an image can't be read, what may not have necessarily
triggered a warning before.