Attempted fix for 0003058: Clicking on view_all_bug_page.php results in 'file download' popup

• config_defaults_inc.php
  (g_compress_html): add a note about coflicts with other compression config
  variable in php.ini

• core/compress_api.php
  (compress_is_enabled): add a check for php.ini methods of enabling compression
  so we don't do it twice

git-svn-id: http://mantisbt.svn.sourceforge.net/svnroot/mantisbt/trunk@2104 <a class="text" href="/?p=mantisbt.git;a=object;h=f5dc347c">f5dc347c</a>-c33d-0410-90a0-b07cc1902cb9