avcodec/dnxhdenc: Fix undefined left shifts of negative numbers

Affected 61 FATE-tests: 60 vsynth tests and lavf-mxf_opatom.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit b7f156e8cb)
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

libavcodec/dnxhdenc.c

@@ -220,7 +220,7 @@ static av_cold int dnxhd_init_vlc(DNXHDEncContext *ctx)
     ctx->vlc_bits  += max_level * 2;
     for (level = -max_level; level < max_level; level++) {
         for (run = 0; run < 2; run++) {
-            int index = (level << 1) | run;
+            int index = level * (1 << 1) | run;
             int sign, offset = 0, alevel = level;
 
             MASK_ABS(sign, alevel);
@@ -610,7 +610,7 @@ void dnxhd_encode_block(DNXHDEncContext *ctx, int16_t *block,
         slevel = block[j];
         if (slevel) {
             int run_level = i - last_non_zero - 1;
-            int rlevel = (slevel << 1) | !!run_level;
+            int rlevel = slevel * (1 << 1) | !!run_level;
             put_bits(&ctx->m.pb, ctx->vlc_bits[rlevel], ctx->vlc_codes[rlevel]);
             if (run_level)
                 put_bits(&ctx->m.pb, ctx->run_bits[run_level],
@@ -690,7 +690,7 @@ int dnxhd_calc_ac_bits(DNXHDEncContext *ctx, int16_t *block, int last_index)
         level = block[j];
         if (level) {
             int run_level = i - last_non_zero - 1;
-            bits += ctx->vlc_bits[(level << 1) |
+            bits += ctx->vlc_bits[level * (1 << 1) |
                     !!run_level] + ctx->run_bits[run_level];
             last_non_zero = i;
         }