[ja] Sync with 8cda28f0a0d3eaa8dee2d5f6df80b22a5635c4e2

Do not advertise unmaintained extensions
[ja] Sync with 05bffa8a995b25c9fc1f31211877baffc4a2d1f6

Do not advertise PEAR as an installation method
[ja] Sync with 2d4941828c318a263de320ec02e11fdc13642bbd

Cleanup upgrading section(s)
[ja] Sync with 12da51e0f9124f25cfa3752388849ffde7161570

Update installation instructions for vfsStream to use Composer
[ja] Sync with 60fe4734e52368ec32a9590c939abffcd4ad8ba5

Rephrase
[ja] Sync with 7c542c865ee5f503aa487b88458e235e9a624981

Leftover from 05bffa8
[ja] Sync with ce95fb069fdb813dc5b679eb4cf6720c1f3aa101

Leftover from 8cda28f
[ja] Sync with e5b1385596c5a4d2d36b2e8a7d2459b9ca4d8b39

Leftover from 05bffa8
[ja] Sync with 634c256b6d2270447f37690112580d8cfb286ef6

assertNotFalse() and assertNotTrue() were introduced in PHPUnit 4.0
[ja] Sync iwth 5d7ec6527075f8b7ddaeb83556ef83200ba66017

More work on documentation for strict mode and risky tests
[ja] Sync with 2f3dbbdccfa68f9cb9e8226f452613b5532559b7
[ja] Sync with f14cb8b1b007914266511cc9ea5eedf9b31e63f5