Add "fall through" comments in switch to disable warning

src/b64/cencode.c

@@ -48,6 +48,7 @@ int base64_encode_block(const char* plaintext_in, int length_in, char* code_out,
 			result = (fragment & 0x0fc) >> 2;
 			*codechar++ = base64_encode_value(result);
 			result = (fragment & 0x003) << 4;
+			/* fall through */
 	case step_B:
 			if (plainchar == plaintextend)
 			{
@@ -59,6 +60,7 @@ int base64_encode_block(const char* plaintext_in, int length_in, char* code_out,
 			result |= (fragment & 0x0f0) >> 4;
 			*codechar++ = base64_encode_value(result);
 			result = (fragment & 0x00f) << 2;
+			/* fall through */
 	case step_C:
 			if (plainchar == plaintextend)
 			{