Adding better support for Windows MBCS (codepages)

Adding better support for some 国家标准 character sets. (ie Chinese standard
character sets), Japanese, Korean and Thai.  Including the Shift-JIS variants.

The characters are displayed at the expected widths.

This does NOT need a specific font as long as the unicode system can find the
requsite characters.

Note the change in the defaults; it is now recommended to explicitly
specify the line character set for DBCS systems.

Also added these Windows charsets to the list.

Unlike DBCS fonts this can be made to work for the Unix port as it only
requires Codepage to Unicode character and width tables.
Reconfigure PuTTY colour scheme from Unix host.

This is possibly related to: /wishlist/colour-scheme.html

These colour schemes are not stored in the PuTTY session file and so
have to be dynamically configured from the host.

The script can read the colour scheme from a Windows PuTTY registry
dump or a Unix session file.
DEBUG messages for tracing