Fix 0003840: Why strip the leading spaces from Description? (applied to all multi-line fields in issue + issue notes).

M core/string_api.php

• Preserve tab by replacing it with 4 non-blank-spaces. This may be made configurable in the future. The rest of the functionality was already implemented but for spaces only.

git-svn-id: http://mantisbt.svn.sourceforge.net/svnroot/mantisbt/trunk@2541 <a class="text" href="/?p=mantisbt.git;a=object;h=f5dc347c">f5dc347c</a>-c33d-0410-90a0-b07cc1902cb9