5.1.1-5.1.4
Merge pull request #2 from sattoke/satBranch

5.1.1-5.1.4
spacing and tiny japanese phrase changes
the double quotation at 'authorization "codes"' just emphasizes "code" as an OAuth protocol parameter, not important here.
modify the translator's note a bit.
tiny spacing and phrase changes
fix xml format to re-enable xml2rfc
4.4.1.1
4.4.1.2 & 4.4.1.3
4.4.1.4