[ticket/10763] Do not call set_post_visibility() statically

PHPBB3-10763
[ticket/10763] Fix static calls to non static methods in colour_manager

PHPBB3-10763
[ticket/10763] Do not call non-static transfer() statically

PHPBB3-10763
[ticket/10763] Do not call messenger::error() statically

PHPBB3-10763
Merge pull request #2101 from nickvergessen/ticket/10763

[ticket/10763] Do not call non-static functions statically