Enh 0003870: Support for custom functions which provides hooks for customizing behaviour

A core/custom_function_api.php

• API providing default implementation for all custom functions.
• Added the first custom function that decides whether a bug should be included in Changelog or not.

M Changelog_page.php

• Use 'changelog_include_issue' custom function to decide if an issue that is visible to the user and that has "fixed in release" set, should be included in changelog or not.

M core.php

• Include custom_functions_inc.php / core/custom_function_api.php.

M core/helper_api.php

• (helper_call_custom_function): This method should be used in all Mantis code to call custom functions. The only case where a custom function is called directly is when it is called from the user's override method.

M .cvsignore

• Added custom_funcitons_inc.php

git-svn-id: http://mantisbt.svn.sourceforge.net/svnroot/mantisbt/trunk@2567 <a class="text" href="/?p=mantisbt.git;a=object;h=f5dc347c">f5dc347c</a>-c33d-0410-90a0-b07cc1902cb9