Fix conversion of EUC-JP-2004 text (and add test suite)

- Truncated multi-byte characters are treated as an error now
- Invalid multi-byte characters are treated as an error rather than
  being quietly swallowed
- ASCII control characters are not allowed to appear in the middle
  of a multi-byte character

Author: alexdowad

ext/mbstring/libmbfl/filters/mbfilter_euc_jp_2004.c

@@ -52,7 +52,7 @@ const struct mbfl_convert_vtbl vtbl_eucjp2004_wchar = {
 	mbfl_filt_conv_common_ctor,
 	NULL,
 	mbfl_filt_conv_jis2004_wchar,
-	mbfl_filt_conv_common_flush,
+	mbfl_filt_conv_jis2004_wchar_flush,
 	NULL,
 };