Added Adlib Gold surround module emulation.

src/sound_ym7128.h

@@ -0,0 +1,25 @@
+typedef struct ym7128_t
+{
+        int a0, sci;
+        uint8_t dat;
+        
+        int reg_sel;
+        uint8_t regs[32];
+        
+        int gl[8], gr[8];
+        int vm, vc, vl, vr;
+        int c0, c1;
+        int t[9];
+        
+        int16_t filter_dat;
+        int16_t prev_l, prev_r;
+        
+        int16_t delay_buffer[2400];
+        int delay_pos;
+        
+        int16_t last_samp;
+} ym7128_t;
+
+void ym7128_init(ym7128_t *ym7128);
+void ym7128_write(ym7128_t *ym7128, uint8_t val);
+void ym7128_apply(ym7128_t *ym7128, int16_t *buffer, int len);