added skeleton for planned i2c API

i2c/i2c.c

@@ -0,0 +1,41 @@
+
+#include <bas_types.h>
+
+void i2c_init(void)
+{
+
+}
+
+void i2c_set_frequency(int hz)
+{
+}
+
+int i2c_read(int address, char *data, int lengt, bool repeated)
+{
+    return 0;
+}
+
+int i2c_read_byte(int ack)
+{
+    return 0;
+}
+
+int i2c_write(int address, const char *data, int length, bool repeated)
+{
+    return 0;
+}
+
+int i2c_write_byte(int data)
+{
+    return 0;
+}
+
+void i2c_start(void)
+{
+
+}
+
+void i2c_stop(void)
+{
+
+}