[ja] Apply bc3f922f2549e44524dc11301d1e53c984b14a1b

The number of hunks is different from the original commit since some changes were already applied to ja translation and, as a result, hunk 20 of original commit became unnecessary.
[ja] Apply 4 commits to ja tree

Hunk 1: e1d6628e2f355577a2d38a9fd93db741631a4a40
Hunk 2: 0c34253095f327209aceab8b3170f93b0c0c4ed9
Hunk 3: 66d1feb527eeb302060e7a67db48816f86ce85e7
Hunk 4: ef5f3e63371b6172c13bb1d51f7f010bca423fa6
[ja] Apply c8571b3b9b7890e6da9d3823c13aed0079e8f257
[ja] Apply fbc3502da99c415d3aa38bcb11758e4e479594de
[ja] Apply bc3f922f2549e44524dc11301d1e53c984b14a1b
Merge pull request #409 from harupong/ja-chapter5

[ja] Update chapter5
[ja] Apply fa4f5a44e26b4a695d65561f6ee4da1954b583ab
[ja] Apply a8203518ecb201bb551586a2ff982832c29ddbd5
Merge pull request #410 from harupong/ja-chapter8

[ja] Update chapter8