Allow handling of word trademarks

Word trademarks are often required to be marked 'on first use'. QDoc could support this by handing a \tm{} command.

\tm

Marks a trademark in running text.

In generated pages, the first occurrence of each trademark outside of a title, section, or link will be specially marked with a ™ postfix. Furthermore, the ™ can be linked to a central page.

Example

\section1 \tm{Android}

For \tm{Android}, Qt does xyzs. for operating systems aside from \tm{Android}, ...

will generate

Android

For Android™, Qt does xzys. for operating systems aside form Android, ...

Related settings

There should be a way to define a generic 'trademarks' page that ™ then links to.

Also, \tm{} would typically be hidden behind a convenient macro, like

macro.Android             = "\tm{Android}"