* addr2line.c (rb_dump_backtrace_with_lines): don't depend hard coded
  symbol '_start'.

* addr2line.c (fill_lines): instead of above, get a dynamic symbol
  in the main executable and use it to know the base address.

* addr2line.c (follow_debuglink0): use obj_info_t instead of
  line_info_t to handle object related data.

* addr2line.c (main_exe_path): defined for Linux.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45493 b2dd03c8-39d4-4d8f-98ff-823fe69b080e