RMDR: libreoffice-5-3 branch created, *remember to cherry-pick* stuff that should go into 5.3.x

Hi *,

as a reminder: libreoffice-5-3 has been created yesterday night.

This marks feature-freeze for LibreOffice 5.3.x, exceptions need to be
approved by ESC members.

While in Beta, no additional review is necessary (so you can
self-approve your bugfixes just like you would on master)

further reading:
https://wiki.documentfoundation.org/ReleasePlan/5.3#5.3.0_release (the schedule)

https://wiki.documentfoundation.org/Development/Branches (the review rules)

So *remember to cherry-pick*.
And tinderbox administrators: please also let your bots build
libreoffice-5-3 branch from now on (and remove libreoffice-5-0 in case
you still have that enabled :-))

ciao
Christian