gdb/dwarf2read.c: rename a field for c++

gdb/dwarf2read.c: rename a field for c++

Fixes:

 ../../src/gdb/dwarf2read.c:127:15: error: declaration of ‘asection* dwarf2_section_info::<anonymous union>::asection’ [-fpermissive]
      asection *asection;
		^
 In file included from ../../src/gdb/common/common-types.h:35:0,
		  from ../../src/gdb/common/common-defs.h:44,
		  from ../../src/gdb/defs.h:28,
		  from ../../src/gdb/dwarf2read.c:31:
 ../bfd/bfd.h:1596:3: error: changes meaning of ‘asection’ from ‘typedef struct bfd_section asection’ [-fpermissive]
  } asection;
    ^

gdb/ChangeLog:
2015-08-21  Tom Tromey  <tromey@redhat.com>

	* dwarf2read.c (struct dwarf2_section_info): Rename field
	'asection' to 'section'.
	(dwarf2_has_info, get_section_bfd_owner, get_section_bfd_section)
	(dwarf2_locate_sections, dwarf2_locate_sections)
	(locate_dwz_sections, locate_v1_virtual_dwo_sections)
	(dwarf2_locate_dwo_sections, dwarf2_locate_dwo_sections)
	(dwarf2_locate_v2_dwp_sections): Adjust.