[RFA 00/42] Remove globals from buildsym

[Tom Tromey <tom at tromey dot com>]

I've long wanted to remove the globals from buildsym and generally
clean it up.  I've finally tackled this project, and this series is
the result.

I'm afraid it is a bit on the long side.  However, I tried to make
each patch relativey small.  Most of them should be easy to review --
and a few are trivial.

Also, I simultaneously wrote this series and learned about some the
workings of buildsym.  So, there are some cases where something is
done -- say, an assertion added or a variable made static -- only to
be un-done later in the series.  Reordering seemed generally painful
so I have left it as is.

The general idea behind the patches is to move each global variable
(or related set of global variables) into the existing
buildsym_compunit structure.  Along the way, some minor cleanups are
done, for example moving stabs-specific things to stabsread.

Once all of the state is in buildsym_compunit, it is put into
buildsym.h for use by symbol readers.  Here, I've converted the DWARF
reader to use the new-style API, leaving the other readers alone.
(The other readers continue to rely on a global, but now only one.)

I haven't tried much to clean up buildsym itself.  The API is just as
unwieldy as ever -- it just no longer has global state.  I have,
however, replaced some data structures with self-managing ones.

There are some holes with the series that you may wish to consider.

* Perhaps some more comments could be added.

* There are still some stabs-specific hacks in buildsym.c that I have
  not attempted to remove.

* There are some remaining calls to set_last_source_file (NULL) that
  could perhaps be removed as unnecessary.  I did not check.

Regression tested by the buildbot.  I also did a reasonable, but not
exhaustive, amount of testing here.  I've at least smoke-tested the
stabs reader by running some tests with --target_board=stabs.

Tom