close handle properly
Fix: Length of guest usernames not checked, refs #836

* inc/datahandlers/post.php
  * added verification of username for guests input using user datahandler
* newreply.php / newthread.php
  * added verification of username for preview
* inc/languages/english/datahandler_post.php
  * added language strings for possible error messages in post author validation
Fixes #892 Incorrect setting on member.php
Fixes #870 Not any last poster (...)

Fixes #870 Not any last poster name in forumdisplay after splitting
a/some post(s)
fix: error message showthread.php?pid=x for deleted posts, refs #947

* showthread.php
  * added check if post with set pid exists before a thread with tid null is searched in the db
Apply changes from #927 directly
Merge pull request #934 from PirataNervo/fix-870

Fixes #870 Not any last poster name in forumdisplay after splitting a/some post(s) (master)
Merge pull request #951 from Nik101010/fix-947

fix: error message showthread.php?pid=x for deleted posts, refs #947
Merge pull request #673 from RageSmirk/patch-3

Close handle properly in captcha.php
Modifies #971 Database fetch_array() Inconsistency
Fixes #330 Permaban Warning Levels don't work
Fixes #325 Thread Prefix Removed During Custom Mod Action
Fixes #936 Wrong compatibility check for plugins
Merge pull request #1035 from PirataNervo/fix-936

Fixes #936 Wrong compatibility check for plugins
Fixes #369 LIMIT clause in session updates
Merge pull request #1037 from PirataNervo/fix-369

Fixes #369 LIMIT clause in session updates
Fixes #338 Spam notification for users with limited administrator permissions but no modera

#338 1.6
Forgot something
Fixes #321 threadsperpage negative value SQL error

#321
Fixes #321 postsperpage negative value SQL error

#321