Fix bfd/dwarf2.c build breakage
    
    Fix build breakage introduced by commit 089e3718bd8d ("Greatly improve
    the speed if looking up DWARF line number information."):
    
     -  bfd_boolean is_linkage;
     -  const char *name;
     -  struct arange arange;
     +  int                  line;
     +  int                  tag;
     +  bfd                  boolean is_linkage;
    
    bfd/ChangeLog:
    2016-11-08  Pedro Alves  <palves@redhat.com>
    
    	* dwarf2.c (struct funcinfo) <is_linkage>: Type is bfd_boolean,
    	not "bfd boolean".