MFC r244437: Support restrict qualifier in dwarf debug info

  Newer clang/llvm emit DW_TAG_restrict_type, which wasn't handled by gdb.
  Import support from Apple's gdb-1822:

  |  2009-03-24  Jason Molenda  (jmolenda@apple.com)
  |
  |    * gdbtypes.c (make_cv_type): Rename this function to make_cvr_type to
  |    also handle restrict qualifiers.
  |    (check_typedef): Handle TYPE_RESTRICT.
  |    * gdbtypes.h (TYPE_FLAG_RESTRICT, TYPE_RESTRICT): New.
  |    * hpread.c (hpread_type_lookup): Update to use make_cvr_type.
  |    * stabsread.c (read_type): Pass the restrict qualifiers along.
  |    * parse.c (follow_types): Pass the restrict qualifiers along.
  |    * dwarf2read.c (read_tag_const_type): Call make_cvr_type.
  |    (read_tag_volatile_type): Same.
  |    (read_tag_restrict_type): New function.
  |    (read_type_die): Handle DW_TAG_restrict_type.

  Obtained from: Apple
MFC r251665: Handle DW_TAG_rvalue_reference_type

  2012-05-21  Jim Ingham <jingham@apple.com>

    * dwarf2read.c (process_die): Handle DW_TAG_rvalue_reference_type.
      (read_type_die): Ditto.
      (dwarf_tag_name): Ditto.

    * elf/dwarf2.h: Add DW_TAG_rvalue_reference_type.

  Obtained from:	Apple, gdb-1820
MFC r251667: Handle DW_TAG_unspecified_type

  2011-11-14  Jim Ingham  <jingham@apple.com>

  * dwarf2read.c (read_type_die): Handle DW_TAG_unspecified_type.
    (read_tag_unspecified_type): New function, add a type for the
    DW_TAG_unspecified_type die.

  Obtained from:	Apple, gdb-1752
MFC r251844: Include die tag in error message