[ticket/12413] Fix: statistics for topics' feed

the absence of parentheses around the calculation erased all that is
before the -1

PHPBB3-12413
[ticket/12413] Fix: the posts were always marked as unapproved

the database return a string, so the strict comparison always returned false

PHPBB3-12413
[ticket/12413] Fix: Soft deleted topics should appear in feeds

As for the posts, a soft deleted topic should appear (with a corresponding
message) in topic's based feeds.

PHPBB3-12413
[ticket/12413] Fix: Differentiating unapproved and deleted posts

Unapproved and deleted posts should not be displayed with the same message
(POST_UNAPPROVED)

PHPBB3-12413
[ticket/12413] Tests: Adding functional tests for the feeds

Some tests are disabled until PHPBB3-12418 (#2331) and PHPBB3-12421 (#2330) are
fixed and merged

PHPBB3-12413
[ticket/12413] Useing @depends to transmit the state of the board

the state of the board is calculate in the first test and transmit to the
others thanks to the @depends annotation.

PHPBB3-12413