patches/gdb: Fix canadian building of GDB for powerpc

Adds patch for GDB v6.8, v7.0, v7.0.1 to fix canadian
cross building of GDB for powerpc.

See original patch information here:
http://sources.redhat.com/bugzilla/show_bug.cgi?id=9638

The patch is not required for GDB v7.1 (fixed).

Tested in canadian combination using mingw32 and powerpc toolchains.
Tested to not affect normal cross building of GDB for powerpc target.

Signed-off-by: Martin Lund <mgl@doredevelopment.dk>

complibs/mpc: add latest version

complibs/gmp: 5.0.0 misses 'EXPERIMENTAL' in the prompt

cc/gcc: baremetal requires a two-pass process

Here, we implement a highly ugly hack. I'm not proud of that one...

To build the libstdc++ library, the compiler requires the C library. In
case we build for non-baremetal, this is normally handled by the final
step, later.

But in the case of bare-metal, we never go through the final step (because
it does not work, and it seems complex enough to make it work), so the
baremetal compilers are issued out of the core step.

libc/newlib: build in the 'start files' pass

A few facts:
- building the C library requires a proper core compiler
- core compiler is issued from one of the core passes
- the C library is required to build libstdc++
- newlib is only built for baremetal
- in bare metal, the final compiler is issued from one of the core passes

So we need to build the C library between core pass 1 and core pass 2.
The only place is eithe libc_headers() or libc_start_files(). The most
pertinent seems to be libc_start_files().

So we build newlib from libc_start_files(), and leave libc() empty.

cc/gcc: store core build rules in an array

Using an array makes it easier to add new rules.
Besides, it is easy to expand from build rules to install rules

cc/gcc: implement default for core options

cc/gcc: fix headers copy for core static

complibs/mpfr: update to latest version

libc/uClibc: apply the threading model to the configuration

The threading model shall be be set in the .config file.
Also, offer the choice between 'old/stable' and 'new' linuxthreads.