Temporarily make TCPDF method _destroyAll() public.
Fixes 'Warning: (Registered shutdown functions) Unable to call TCPDF::_destroyAll() - function does not exist in Unknown on line 0'

Signed-off-by: Madhura Jayaratne <madhura.cj@gmail.com>
Merge branch 'master' of github.com:phpmyadmin/phpmyadmin