Qdoc mangles link targets that contain trademark symbols

Llinks to section titles with a special character (trademark symbols) fail. Qt for MCUs has a lot of section titles with trademark symbols, and these link targets are mangled with you build with qdoc 6.9, leading to broken links. For example, the Flashing Instructions for Infineon boards topic has several subsections with ™ symbol in the title. In the latest qdoc manual, the \tm command that adds the trademark symbol, recommends not to use it in section titles or it doesn't have any effect when used in \section titles. It would be useful if qdoc warnings include info. about why the link failed than just saying it failed.