adjust indent
remove invisible dummy message number at beginning-of-line

Mew 6.x does not need message number at beginning-of-line.
It seems to be even harmful.
Introduce ``X-SC-Recurrence-Tag:''
Convert encoding to UTF-8
Remove trailing whitespaces
Expand tab to 8 spaces
Default coding-system to UTF-8
Add mhc-goto-next/previous-year
Add mhc-import-from-region
Add .gitignore
Merged from upstream.