class THtml::TFileDefinition: public THtml::THelperBase

 Create all permutations of path and THtml's input path:
 path being PP/ and THtml's input being .:include/:src/ gives
 .:./PP/:include:include/PP/:src/:src/PP

 Given a class name with a scope, split the class name into directory part
 and file name: A::B::C becomes module B, filename C.

 Determine cl's declaration file name. Usually it's just
 cl->GetDeclFileName(), but sometimes conversions need to be done
 like include/ to abc/cde/inc/. If no declaration file name is
 available, look for b/inc/C.h for class A::B::C. out_fsys will contain
 the file system's (i.e. local machine's) full path name to the file.
 The function returns false if the class's header file cannot be found.

 If your software cannot be mapped into this scheme then derive your
 own class from TFileDefinition and pass it to THtml::SetFileDefinition().

 Determine cl's implementation file name. Usually it's just
 cl->GetImplFileName(), but sometimes conversions need to be done.
 If no implementation file name is available look for b/src/C.cxx for
 class A::B::C. out_fsys will contain the file system's (i.e. local
 machine's) full path name to the file.
 The function returns false if the class's source file cannot be found.

 If your software cannot be mapped into this scheme then derive your
 own class from TFileDefinition and pass it to THtml::SetFileDefinition().

 Common implementation for GetDeclFileName(), GetImplFileName()