Cleanup on the unified section list changes. Main changes are:
- ObjectFile::GetSymtab() and ObjectFile::ClearSymtab() no longer takes any flags
- Module coordinates with the object files and contain a unified section list so that object file and symbol file can share sections when they need to, yet contain their own sections.

Other cleanups:
- Fixed Symbol::GetByteSize() to not have the symbol table compute the byte sizes on the fly
- Modified the ObjectFileMachO class to compute symbol sizes all at once efficiently
- Modified the Symtab class to store a file address lookup table for more efficient lookups
- Removed Section::Finalize() and SectionList::Finalize() as they did nothing
- Improved performance of the detection of symbol files that have debug maps by excluding stripped files and core files, debug files, object files and stubs
- Added the ability to tell if an ObjectFile has been stripped with ObjectFile::IsStripped() (used this for the above performance improvement)