stream: use char instead of uint8_t

src/stream.h

@@ -5,8 +5,8 @@
 #include <stdint.h>
 
 typedef struct {
-    void (*write)(const uint8_t * src, size_t length);
-    void (*write1)(uint8_t c);
+    void (*write)(const char * src, size_t length);
+    void (*write1)(char c);
 } stream_t;
 
 #endif