[ticket/10945] remove trigger_error call

removes trigger_error call incase no search results are found or start
variable exceeds the amount. So that search query is displayed in the
search box even if no results are returned.

PHPBB3-10945
[ticket/10945] Display search query when search fails in native search

If search fails and common words are present, split_keywords returns false
and search.php file prints appropriate message of common words.
If search fails and there are no common words, split_keywords returns true
and keyword_search returns false so that the search query is displayed in
search box.

PHPBB3-10945
[ticket/10945] Fix return values for split_keywords function

The function now returns false if all the words are common words and true
otherwise.

PHPBB3-10945
Merge remote-tracking branch 'remotes/dhruvgoel92/ticket/10945' into develop-olympus

* remotes/dhruvgoel92/ticket/10945:
  [ticket/10945] Fix return values for split_keywords function
  [ticket/10945] Display search query when search fails in native search
  [ticket/10945] remove trigger_error call
[ticket/10549] Adds language variables

PHPBB3-10549
[ticket/12106] Adds a explaination that admin/mods still able to use the board

PHPBB3-12106
[ticket/12106] Combined first and second sentence

PHPBB3-12106
Merge pull request #2100 from Crizz0/ticket/10549

[ticket/10549] Adds language variables to Error messages MODULE...
Merge pull request #2105 from Crizz0/ticket/12106

[ticket/12106] Adds a explaination that admin/mods still able to use the...