This patch adds dwarf2_frame_state_reg_info ctor, dtor, copy ctor,
assignment operator, and move assignment. This patch also adds unit test
to execute_cfa_program to cover the changes.
[GDB_SELF_TEST]: Include selftest.h and
selftest-arch.h.
[GDB_SELF_TEST] (execute_cfa_program_test): New function.
(_initialize_dwarf2_frame) [GDB_SELF_TEST]: Register
execute_cfa_program_test.