alsdec: Check that quantized parcor coeffs are within range.

ALS spec:
	11.6.3.1.1 Quantization and encoding of parcor coefficients
	...
	In all cases the resulting quantized values ak are restricted to the range [-64,63].

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
Signed-off-by: Justin Ruggles <justin.ruggles@gmail.com>

libavcodec/alsdec.c

@@ -705,6 +705,10 @@ static int read_var_block_data(ALSDecContext *ctx, ALSBlockData *bd)
                     int rice_param = parcor_rice_table[sconf->coef_table][k][1];
                     int offset     = parcor_rice_table[sconf->coef_table][k][0];
                     quant_cof[k] = decode_rice(gb, rice_param) + offset;
+                    if (quant_cof[k] < -64 || quant_cof[k] > 63) {
+                        av_log(avctx, AV_LOG_ERROR, "quant_cof %d is out of range\n", quant_cof[k]);
+                        return AVERROR_INVALIDDATA;
+                    }
                 }
 
                 // read coefficients 20 to 126