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

--- gcc-4.1.2.orig/gcc/Makefile.in	2006-11-01 15:40:44.000000000 +0100

+++ gcc-4.1.2/gcc/Makefile.in	2007-03-04 23:34:32.000000000 +0100

@@ -2522,7 +2522,7 @@

 # FIXME: writing proper dependencies for this is a *LOT* of work.

 libbackend.o : $(OBJS-common:.o=.c) $(out_file) \

   insn-config.h insn-flags.h insn-codes.h insn-constants.h \

-  insn-attr.h  $(DATESTAMP) $(BASEVER) $(DEVPHASE)

+  insn-attr.h  $(DATESTAMP) $(BASEVER) $(DEVPHASE) gcov-iov.h

 	$(CC) $(ALL_CFLAGS) $(ALL_CPPFLAGS) \

 	  -DTARGET_NAME=\"$(target_noncanonical)\" \

 	  -DLOCALEDIR=\"$(localedir)\" \