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

 source "config/backend.in"

 source "config/global.in"

 source "config/target.in"

 source "config/toolchain.in"

 source "config/kernel.in"

 source "config/binutils.in"

 source "config/cc.in"

 source "config/libc.in"

 source "config/debug.in"

 source "config/companion_libs.in"

 source "config/companion_tools.in"