avcodec/fitsdec: Use lrint()

Fixes: fate-fitsdec-bitpix-64

Possibly Fixes: -nan is outside the range of representable values of type 'unsigned short'
Possibly Fixes: 17769/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_FITS_fuzzer-5678314672357376

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpegSigned-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/fitsdec.c

@@ -279,7 +279,7 @@ static int fits_decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
             for (j = 0; j < avctx->width; j++) { \
                 t = rd; \
                 if (!header.blank_found || t != header.blank) { \
-                    *dst++ = ((t - header.data_min) * ((1 << (sizeof(type) * 8)) - 1)) * scale; \
+                    *dst++ = lrint(((t - header.data_min) * ((1 << (sizeof(type) * 8)) - 1)) * scale); \
                 } else { \
                     *dst++ = fitsctx->blank_val; \
                 } \

tests/ref/fate/fitsdec-bitpix-32

@@ -3,4 +3,4 @@
 #codec_id 0: rawvideo
 #dimensions 0: 102x109
 #sar 0: 0/1
-0,          0,          0,        1,    22236, 0x34490902
+0,          0,          0,        1,    22236, 0x24634517

tests/ref/fate/fitsdec-bitpix-64

@@ -3,4 +3,4 @@
 #codec_id 0: rawvideo
 #dimensions 0: 77x173
 #sar 0: 0/1
-0,          0,          0,        1,    26642, 0x0ad2a46a
+0,          0,          0,        1,    26642, 0xa9eec634

tests/ref/fate/fitsdec-blank_bitpix32

@@ -3,4 +3,4 @@
 #codec_id 0: rawvideo
 #dimensions 0: 256x256
 #sar 0: 0/1
-0,          0,          0,        1,   131072, 0x7fb22427
+0,          0,          0,        1,   131072, 0x3ecd0739

tests/ref/fate/fitsdec-ext_data_min_max

@@ -3,4 +3,4 @@
 #codec_id 0: rawvideo
 #dimensions 0: 512x512
 #sar 0: 0/1
-0,          0,          0,        1,   524288, 0xc327ed23
+0,          0,          0,        1,   524288, 0x6567ecb3

tests/ref/fate/fitsdec-gray

@@ -3,4 +3,4 @@
 #codec_id 0: rawvideo
 #dimensions 0: 128x128
 #sar 0: 0/1
-0,          0,          0,        1,    16384, 0xd788a2d2
+0,          0,          0,        1,    16384, 0x353dbacd

tests/ref/lavf/gray16be.fits

 15e85a553bbd07783f92377ed369308b *tests/data/lavf/lavf.gray16be.fits
 5184000 tests/data/lavf/lavf.gray16be.fits
-tests/data/lavf/lavf.gray16be.fits CRC=0x8b840cff
+tests/data/lavf/lavf.gray16be.fits CRC=0x8cdcbeb2