Consistent display of "<optimized out>" for register values.

Consistent display of "<optimized out>" for register values.

  https://sourceware.org/ml/gdb-patches/2013-08/msg00170.html

gdb/ChangeLog

        * infcmd.c (default_print_one_register_info): Add detection of
        optimized out values.
        (default_print_registers_info): Switch to using
        get_frame_register_value.

gdb/testsuite/ChangeLog

        * gdb.dwarf2/dw2-reg-undefined.exp: Change pattern for info
        register to "<optimized out>", and also print the registers.