Fix and update D demangling support in gdb to the current mangling ABI.

Fix and update D demangling support in gdb to the current mangling ABI.

gdb/ChangeLog:
2014-01-17  Iain Buclaw  <ibuclaw@gdcproject.org>

    * d-lang.h (d_parse_symbol): Add declaration.
    * d-lang.c (extract_identifiers)
    (extract_type_info): Remove functions.
    (parse_call_convention, parse_attributes)
    (parse_function_types, parse_function_args)
    (parse_type, parse_identifier, call_convention_p)
    (d_parse_symbol): New functions.
    (d_demangle): Use d_parse_symbol to demangle D symbols.

gdb/testsuite/ChangeLog:
2014-01-17  Iain Buclaw  <ibuclaw@gdcproject.org>

* gdb.dlang/demangle.exp: New file.