"UPDATE LOG" still doesn't match the underlining when translated

[SergeyBiryukov]

This is a follow-up to #26621.

1. [26883] didn't actually fix it, strlen() doesn't work as expected for multibyte strings:

   ЖУРНАЛ ОБНОВЛЕНИЯ
   =================================
   

   We should just make the whole header translatable, like the one in "Beta Testing?" section: tags/3.9.1/src/wp-admin/includes/class-wp-upgrader.php#L2517​.

2. Background update failure email has two line breaks before the "Beta Testing?" section, but none after it:

   FAILED: WordPress failed to update to WordPress 4.0-alpha-20140518
   
   
   BETA TESTING?
   =============
   
   This debugging email is sent when you are using a development version of WordPress.
   
   If you think these failures might be due to a bug in WordPress, could you report it?
    * Open a thread in the support forums: https://wordpress.org/support/forum/alphabeta
    * Or, if you're comfortable writing a bug report: http://core.trac.wordpress.org/
   
   Thanks! -- The WordPress Team
   UPDATE LOG
   ==========
   
   WordPress 4.0-alpha-20140518
   ----------------------------
     Updating to WordPress 4.0-alpha-20140518
     Downloading update from https://wordpress.org/nightly-builds/wordpress-latest.zip...
     Installation Failed
     Error: [download_failed] Download failed.
            Operation timed out after 300000 milliseconds with 2830099 out of 8299181 bytes received
   

[SergeyBiryukov]

28306.patch​ should fix both issues.

[SergeyBiryukov]

In 28537:

Fix inconsistent header underlining and spacing in background update emails.

fixes #28306.