crossgcc: Update toolchain

New tools:
* mpfr 3.1.4
* binutils 2.26
* gcc 5.3.0
* llvm/clang 3.8.0

Patch changes:
* binutils-2.25_fix-aarch64.patch: fixed in 2.26
* binutils-2.25_host-clang.patch: the positions of header file
  includes have been adjusted
* binutils-2.25_no-bfd-doc.patch: update to 2.26
* binutils-2.25_riscv.patch: update from riscv-gnu-toolchain
* gcc-5.2.0_elf_biarch.patch: update to 5.3.0
* gcc-5.2.0_gnat.patch: update to 5.3.0
* gcc-5.2.0_libgcc.patch: update to 5.3.0
* gcc-5.2.0_nds32.patch: update to 5.3.0
* gcc-5.2.0_riscv.patch: update from riscv-gnu-toolchain
* cfe-3.7.1.src_frontend.patch: update to 3.8.0

In the latest code of riscv-gnu-toolchain project, the patch for
{binutils,gcc}/config.sub has been removed, and the target is renamed
as riscv32 and riscv64. The `riscv' to `riscv64' change in xcompile is
in another commit.

Test results:
All GCC and LLVM/clang toolchain build successfully.

x86,arm: qemu boots
power8: firmware fails to boot
aarch64,mips: not tested
riscv: firmware fails to build with new binutils
clang: firmware fails to boot

Signed-off-by: Iru Cai <mytbk920423@gmail.com>
Change-Id: I42ce89c29263d768d161c28199994f17d0389633
Reviewed-on: https://review.coreboot.org/14227
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

util/crossgcc/patches/gcc-5.3.0_gnat.patch

@@ -0,0 +1,11 @@
+--- gcc-5.3.0/gcc/ada/gcc-interface/Make-lang.in.bak	2015-08-24 16:23:25.004493665 +0200
++++ gcc-5.3.0/gcc/ada/gcc-interface/Make-lang.in	2015-08-24 17:53:52.496636113 +0200
+@@ -45,7 +45,7 @@
+ 
+ 
+ # Extra flags to pass to recursive makes.
+-COMMON_ADAFLAGS= -gnatpg
++COMMON_ADAFLAGS= -gnatpg -gnatwG
+ ifeq ($(TREECHECKING),)
+ CHECKING_ADAFLAGS=
+ else