For a few of the supported architectures we can use one-to-one mapping
from the dwarf to the libunwind register numbers. Allow the
architectures to define their own dwarf_to_unw_regnum() macro to do this
easily.
include/dwarf.h: Declare dwarf_reg_state_pool and dwarf_cie_info_pool.
include/dwarf_i.h: Include libunwind_i.h instead of tdep.h.
Make dwarf_to_unw_regnum() a macro so it doesn't get compiled
into an object file merely because it include dwarf_i.h (important
when optimization is turned off).
(dwarf_read_encoded_pointer_inlined): New function.
include/tdep-x86/libunwind_i.h: Add include of "mempool.h".
include/tdep-x86_64/libunwind_i.h: Add include of "mempool.h".
