avcodec/qtrleenc: Fix memleak upon allocation failure

The qtrle encoder allocates several buffers and an AVFrame in its init
function. If one of these allocations fails, but others succeed, the
successfully allocated objects leak. This is fixed by setting the
FF_CODEC_CAP_INIT_CLEANUP flag.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
(cherry picked from commit 2a71cbeb019fabd70f04ca9d2ec5d0bff3b3e3d2)

libavcodec/qtrleenc.c

@@ -413,4 +413,5 @@ AVCodec ff_qtrle_encoder = {
     .pix_fmts       = (const enum AVPixelFormat[]){
         AV_PIX_FMT_RGB24, AV_PIX_FMT_RGB555BE, AV_PIX_FMT_ARGB, AV_PIX_FMT_GRAY8, AV_PIX_FMT_NONE
     },
+    .caps_internal  = FF_CODEC_CAP_INIT_CLEANUP,
 };