pollution when compiling with debugging enabled. The name-space
pollution came from the fact that functions won't be inlined in this
case and that ended up generating dead code with references to
non-existent functions.
(Logical change 1.154)
(regname_len): New macro.
(regname_str): New macro.
(NREGS): New macro.
(unw_regname): Change it from using a regname[] array to using
a single string.
(Logical change 1.148)