Proposal: DW_TAG_restrict_type per ISO C9X

===Summary
Add DW_TAG_restrict_type for ISO C9X

This is new in C9X and while it is not essential
for a debugger to use, it is nice to be
able to report the correct qualifiers to users.

===Current Specification
does not mention the new qualifier

===Proposed Modification to the document.

page 38, Sec 5.2: Type Modifier Entries

add
DW_TAG_restrict_type     C     restrict qualified type

Change the second example to

volatile char * const restrict p;
DW_TAG_restrict_type ->
  DW_TAG_const_type ->
    DW_TAG_pointer_type ->
      DW_TAG_volatile_type ->
        DW_TAG_base_type


Figure 14, page 68, add the tag to the list with the
next available value (perhaps 0x36).

Page88, Appendix 1, add
        DW_TAG_restrict_type          DW_AT_sibling
                                     DW_AT_type