Make various lm_info implementations inherit from a base class
The lm_info structure is used to store target specific information about
mapped libraries. It is currently defined as an opaque type in solist.h
and a pointer to it is included in solist, the target-agnostic object
representing a loaded shared library. Multiple targets define their own
implementation of lm_info.
In anticipation of using C++ stuff (e.g. vector) in the lm_info objects,
we first need to avoid different definitions of classes with the same
name (which violates the one definition rule). This patch does it by
having a base class (lm_info_base) from which all the specific lm_info
derive. Each implementation is renamed to something that makes sense
(e.g. lm_info_aix for AIX). The next logical step would probably be to
derive directly from so_list, it's not really obvious, so I'll keep that
for another day.
One special case is the Neutrino (nto) support. It uses SVR4-style
libraries, but overrides some methods. To do that, it needed to have
its own copy of SVR4's lm_info structure in nto-tdep.c, because it was
just not possible to put it in solib-svr4.h and include that file. Over
time, that copy got out of sync, which is still the case today. I can
only assume that the lm_addr function in nto-tdep.c is broken right now.
The first field of the old lm_info was a pointer (gdb_byte *), whereas
in the new lm_info it's an address in the inferior (CORE_ADDR). Trying
to use that field today probably results in a crash. With this
refactor, it's now possible to put lm_info_svr4 in solib-svr4.h and just
include it. I have adapted the code in nto-tdep.c to that it builds,
but it's probably not correct. Since I don't have the knowledge nor
setup to try this on Neutrino, somebody else would have to fix it. But
I am confident that I am not making things worse than they already are.