UTF-8 encoding bug on PHP older than 5.4

In PHP older than 5.4.0, the default charset for htmlspecialchars() and
html_entity_decode() was ISO-8859-1, which created erroneous UTF-8
characters
More explicit UTF-8

More explicit UTF-8 in PDO MySQL, html_entity_decode, htmlentities, and
htmlspecialchars (less important)
Another explicit UTF-8

Explicit UTF-8 for a forgotten htmlentities()
Revert wrong change on array_map

But would still be better with explicit UTF-8
Merge branch 'utf8bug' of https://github.com/Alkarex/FreshRSS into Alkarex-utf8bug