• core/custom_field_api.php
  (custom_field_cache_row): new function to cache field definitions
  (custom_field_clear_cache): new function to clear field definition caches
  (custom_field_exists): reimplement using custom_field_cache_row()
  (custom_field_has_read_access): remove warnings by actually getting the access_level_r variable
  (custom_field_has_write_access): remove warnings by actually getting the access_level_rw variable
  (custom_field_update): call custom_field_clear_cache()
  (custom_field_destroy): call custom_field_clear_cache()
  (custom_field_get_definition): reimplement as a call to custom_field_cache_row()
  (custom_field_get_field): new function to get a single db field from a field definition

Add field definition caching to custom fields and finish implementation of custom_fieldhas*_access
() functions so they don't give warnings anymore

git-svn-id: http://mantisbt.svn.sourceforge.net/svnroot/mantisbt/trunk@1733 <a class="text" href="/?p=mantisbt.git;a=object;h=f5dc347c">f5dc347c</a>-c33d-0410-90a0-b07cc1902cb9