Fix inter-class and intra-class cross-reference issues that appeared with Doxygen 1.9.7 caused partially by the presence of the same-named ktxTexture macro. Fixed by changing TYPEDEF_HIDES_STRUCT from YES to NO in config.
Fix intra-class ktxTexture references broken due to presence of the same-named ktxTexture macro. Fixed by using fully qualified "class" names.
Fix many, but by no means all, of the remaining references broken by Doxygen 1.9.6's requirement for fully qualified "class" names for inter-class references.
Move methods incorrectly labelled as belonging to ktxTexture to their correct ktxTexture1 "class".
Restore Topics item to Doxygen navindex for access to the *Loader, Reader and Writer groups.
Remove confusions caused by use of @copydetails across classes.