Audit use of return-by-reference

[wonderboymusic]

(The component for this ticket is Performance because nothing else made any sense)

This has come up in other tickets, and each time it has been recommended that we remove the return by reference indicators when present on functions and class methods. From php.net:

Do not use return-by-reference to increase performance. The engine will automatically optimize this on its own. Only return references when you have a valid technical reason to do so.

Is there a valid technical reason to still do so? Since PHP5, objects are always passed by reference.

[ryan]

In [21792]:

Remove unnecessary return by refs. Props wonderboymusic. fixes #21839

[SergeyBiryukov]

[21792] totally broke i18n: 21839.i18n.png​. 21839.mo.diff​ fixes that.

[wonderboymusic]

eek, sorry bout that

[ryan]

In [21793]:

Restore return by ref for make_entry(). Props SergeyBiryukov. fixes #21839