[fix] tighten pseudo HTML tag parser
[fix] tighten pseudo HTML tag parser

 - opening and closing tags have to match _exactely_
 - closing tag is only accepted if it matches a previous
   opening tag
 - color tag has to match exactely
 - color must have _exactely_ six hex digits

Signed-off-by: David Oberhollenzer <ef97309e490485c1bad5018f0617d7fa37bc07ac@tele2.at>

AgentD/sgui,AgentD/sgui,AgentD/sgui