MTDURLPreview doesn't respect "Content-Type" charset

[AHgPuK]

Pages which are encoded with non-UTF8 encoding are shown incorrectly especially for languages having several encoding usages in a country.
For example, Russia has at least 6 different charsets for a text encoding:
Windows CP1251, DOS-866, DOS-855, KOI8-R, ISO-8859-5, Cyrillic Mac
Each one has its own encoding charset.
It should be respected by detecting "Content-Type" header and meta http-equiv="Content-Type"