proposed symbol format deprecations

[Tom Tromey]

I've been working on some changes that touch most of the symbol readers,
and I notice that a couple of them are barely active -- somread.c and
mdebugread.c.

somread.c is used to read the HP-UX SOM format:

    http://en.wikipedia.org/wiki/System_Object_Model_%28file_format%29

It is only used on 32-bit PA-RISC systems.  somread.c can't even be
built on other machines as it requires the HP-UX <syms.h>.


mdebugread.c is used to read the ECOFF format:

    http://en.wikipedia.org/wiki/ECOFF

It is most recently used, I think, by Tru64.


I would like to propose deprecating both of these readers.

I think somread.c hasn't been actively developed in some time.  32-bit
PA-RISC machines seem hard to come by nowadays.

mdebugread.c also seems unused.  I recently discovered that it doesn't
use buildsym to make blocks, so with the "global_block" changes it will
probably cause gdb crashes if it is actually used.  (It also leaks all
the blocks it creates ... quite bad.)


Specifically I propose that we announce the deprecations in NEWS and
remove the files from the build (but leave them in the source tree) for
gdb 7.6.  Then, after 7.6 is out, we remove the files from trunk.

If someone steps forward to maintain the code, we can easily resurrect
it.

Tom