Integrate new symtab reader into corpus and read_context

While reading the corpus in the read_context, also load the new type
symtab object side-by-side and set it accordingly in the resulting
corpus. This is still side by side and passive code that gets active in
the following changes. This is applicable for the dwarf reader as well
as for the reader that consumes XML.

	* include/abg-corpus.h (corpus::set_symtab): New method declaration.
	  (corpus::get_symtab): New method declaration.
	* include/abg-fwd.h (symtab_reader::symtab_sptr): New forward
	  declaration.
	* src/abg-corpus-priv.h (corpus::priv::symtab_): New data member.
	* src/abg-corpus.cc
	  (corpus::set_symtab): Likewise.
	  (corpus::get_symtab): Likewise.
	* src/abg-dwarf-reader.cc (read_context::symtab_): New data member.
	  (read_context::initialize): reset symtab_ as well
	  (read_context::symtab): new method that loads a symtab on
	  first access and returns it.
	  (read_debug_info_into_corpus): also set the new symtab object
	  on the current corpus.
	  (read_corpus_from_elf): Also determine (i.e. load) the new
	  symtab object and contribute to the load status.
	* src/abg-reader.cc (read_corpus_from_input): also set the new
	  type symtab when reading from xml.
	* tests/test-symtab.cc: Add test assertions.

Reviewed-by: Giuliano Procida <gprocida@google.com>
Signed-off-by: Matthias Maennich <maennich@google.com>
Change-Id: I3210c628c1b1f370cccc4e0730051612b3e4b36f
9 files changed