SVN: Create branch from trunk@61437 to restore files from build change.

In [61438], a number of required PHP files were deleted from the repo and then added to the `.gitignore` file, severing their version history in the project.

This commit creates a new branch from before that change which will be used to reassociate the history for those files with their restored versions.

Discussed in: https://core.trac.wordpress.org/ticket/64393

Props desrosj, dmsnell.
See #64393.


git-svn-id: https://develop.svn.wordpress.org/branches/fixes-64393-restore-version-history@61863 602fd350-edb4-49c9-b593-d223f7449a82