dbghelp: Create new infrastructure to hold specific information for multiple file/debug formats in a single module, and use it to store dwarf2 stuff.

dbghelp: Now that we can keep ELF sections around, don't copy the loclist section, just don't unmap it.

dbghelp: Keep the file map around for every PE module, so that we can access image whenever we like to.

dbghelp: Extend the ELF image management to PE modules so we get a rather uniform interface to image manipulation.