avutil/mathematics: Fix undefined negation in av_compare_ts()

Fixes: negation of -9223372036854775808 cannot be represented in type 'int64_t' (aka 'long'); cast to an unsigned type to negate this value to itself
Fixes: 29437/clusterfuzz-testcase-minimized-ffmpeg_dem_MOV_fuzzer-4748510022991872

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

libavutil/mathematics.c

@@ -148,7 +148,7 @@ int av_compare_ts(int64_t ts_a, AVRational tb_a, int64_t ts_b, AVRational tb_b)
 {
     int64_t a = tb_a.num * (int64_t)tb_b.den;
     int64_t b = tb_b.num * (int64_t)tb_a.den;
-    if ((FFABS(ts_a)|a|FFABS(ts_b)|b) <= INT_MAX)
+    if ((FFABS64U(ts_a)|a|FFABS64U(ts_b)|b) <= INT_MAX)
         return (ts_a*a > ts_b*b) - (ts_a*a < ts_b*b);
     if (av_rescale_rnd(ts_a, a, b, AV_ROUND_DOWN) < ts_b)
         return -1;