writeU8 is unused in the external libcdr lib, but filter it out from easy

Makefile

@@ -485,6 +485,7 @@ findunusedcode:
               | grep -v ^WP6 \
               | grep -v ^WPG \
               | grep -v ^WPS \
+              | grep -v WPXBinaryData \
               > unusedcode.easy
 
 check: dev-install subsequentcheck

unusedcode.easy

-(anonymous namespace)::writeU8(WPXBinaryData&, int)
 CertificateExtension_XmlSecImpl::setCertExtn(com::sun::star::uno::Sequence<signed char>, com::sun::star::uno::Sequence<signed char>, unsigned char)
 CharPosArray::Insert(CharPosArray const*, unsigned short, unsigned short, unsigned short)
 CharPosArray::Replace(int const&, unsigned short)