[RFC: 0/9] No context-switching

[Pedro Alves <pedro@codesourcery.com>]

This series of patches removes inferior control globals, in favour of 
accessing thread_info members directly, effectivelly, getting rid of
the need to context-switch.

I've layed out the series so it is always functional at all of
its incremental steps.  At the end of the series, context_switch will
just be a wrapper around switch_to_thread.  I still left that function
around, mainly, for "set debug infrun 1" purposes (it prints an
useful message).

I've tested the whole series on x86_64-unknown-linux-gnu,
i386-unknown-openbsd4.3, i386-pc-solaris2.11, i686-pc-cygwin,
and arm-none-linux-gnu (to cover software single-step), I found no
regressions.

This series depends on having all targets register the main thread
in the the thread list, even when debugging a single-threaded
inferior.  Patches for most of the targets have been posted
already, most approved.

I believe the only missing targets to adjust are AIX,
remote-mips.c, nto-procfs.c.  I've talked with Aleksandar about
nto, and we came to the conclusion that nto is easy to fix.
remote-mips.c should be as similarly easy to remote-m32-sdi.c,
monitor.c or remote-sim.c.  I'll try to give another look at
AIX this weekend, and browse over IBM's documentation, to see if
I can come up with an initial patch, but it doesn't seem likelly,
with no AIX access.

In the mean time, I thought I'd post this series as an RFC.

-- 
Pedro Alves