fixup! git tag --contains : avoid stack overflow

Signed-off-by: Stepan Kasal <kasal@ucw.cz>
Merge pull request #169 from kasal/master

fixup! git tag --contains : avoid stack overflow
fixup! Windows: Always normalize paths to Windows-style
Merge pull request #175 from kasal/normalize-win-paths

fixup! Windows: Always normalize paths to Windows-style
Enable Python by default on MINGW
Convert charactor encoding to utf-8 on MINGW before git fast-import

System default in Japanese Language version
 * p4: CP932 on Windows
 * msysgit: UTF-8 on Windows(MINGW)
Cosmetic change
Improve conversion of character encoding

- Make use of P4CHARSET environment variable
- Make use of encode method with ignore option
Add URLs to refer to character encodings

 * http://www.perforce.com/perforce/doc.current/user/i18nnotes.txt
 * http://docs.python.org/2.7/library/codecs.html#standard-encodings
Improve conversion of character encoding when p4 submit

- Convert character encoding of logMessage to P4CHARSET or to a encoding
  from user preferences, appropriately
- Separate p4char2encode hash from tounicode function, accordingly
- Use the Codec instead of Aliases in Python Standard Encodings

https://docs.python.org/2.7/library/codecs.html#standard-encodings
- Distinguish decoded data and data
- Make debug print conditionally