value_fetch_lazy, ensure parent is not lazy and check parent for validity.

value_fetch_lazy, ensure parent is not lazy and check parent for validity.

  http://sourceware.org/ml/gdb-patches/2013-07/msg00316.html

gdb/ChangeLog

        * value.c (value_fetch_lazy): Ensure parent value is not lazy
        before checking which bits of the parent, not the child, value are
        valid.

gdb/testsuite/ChangeLog

        * gdb.dwarf2/pieces-optimized-out.exp: New file.
        * gdb.dwarf2/pieces-optimized-out.c: New file.
        * gdb.dwarf2/pieces-optimized-out.S: New file.