cc/gcc: fix building for powerpc for the 4.4.x series

Reported by: Thomas Petazzoni
http://sourceware.org/ml/crossgcc/2010-03/msg00057.html

Discussions:
http://lists.uclibc.org/pipermail/uclibc/2010-March/043697.html
http://lists.uclibc.org/pipermail/buildroot/2010-March/032790.html
http://ibot.rikers.org/%23uclibc/20100316.html.gz
(search for "copysignl", by kos_tom, blindvt and y_morin)

binutils/sstrip: get rid of ELFkickers

ELFkickers are looong dead and unmaintained, and the sstrip
from buildroot is working fine *and* is maintained.

binutils/sstrip: depends on ELF

No point building sstrip is the target is not ELF.

tools: move sstrip to the binary utilities menu

sstrip is now alone in its 'tools' menu, and we will probably never gain
any other 'tool'. Besides, sstrip is just strip, but a little bit more
agressive, so it deserves going to the 'binary utilities' menu.

debug/gdb: gdb>=7.0 can use MPC, enable for cross-gdb

debug/gdb: add handling of 7_0_or_later

We'll need to differentiate gdb 7.0 or later, from gdb prior to 7.0

debug/gdb: add option to use GMP and MPFR

GMP and MPFR are optional for gdb, so offer a config option.

debug/gdb: can't build a static native gdb if using GMP/MPFR

It is currently impossible to reliably build static GMP/MPFR libs,
so we can't build a static native gdb using them, obviously.

debug/gdb: split menuconfig for easier maintenance

cc/gcc: fix use of companion libraries