Add basic support for the Blackfin architecture

For uClibc, the name of the Blackfin architecture is 'bfin'. Actually,
the naming of the architecture is quite messy: for toolchain tuples
and uClibc, it's bfin, but for the kernel, it's blackfin. We've
arbitraly choosen to name it "blackfin" in Crosstool-NG.

Add Blackfin-related uClibc patch to fix a build failure related to
fork() being used in unistd/daemon.c.

Yann E. MORIN:
Apply the patch to the kernel/linux build script to use 'linux'
in the noMMU tuples. See:
http://sourceware.org/ml/crossgcc/2010-04/msg00010.html

# x86 specific options

config ARCH_x86

    select ARCH_SUPPORTS_32

    select ARCH_SUPPORTS_64

    select ARCH_DEFAULT_32

    select ARCH_USE_MMU

    select ARCH_SUPPORT_ARCH

    select ARCH_SUPPORT_CPU

    select ARCH_SUPPORT_TUNE

    help

      The x86 architecture, as defined by:

        32-bit (ia32) : http://www.intel.com/

        64-bit (amd64): http://www.amd.com/us-en/Processors/DevelopWithAMD/0,,30_2252_875_7044,00.html