panels 6.x-3.5

This release is primarily a follow-up quickfix to problems in the 6.x-3.4 release.

Changes since DRUPAL-6--3-4:

• Restored (and deprecated) panels_print_layout(), as other modules were
  relying on it.
• Increment required CTools API version.
• Updated docblock to indicate when the deprecated panels_load_include()
  will be removed.
• Deincrement required CTools API version; should only increment once
  changes have been introduced that necessitate it.
• Updated CHANGELOG for release.
• Replace panels_load_include() with ctools_include().
• Restore panels_load_include() as there are other modules that use this function and broke without it.