buildgcc: Update GCC, Binutils, GMP, MPFR, GDB, IASL and LLVM

- GCC gets updated from 5.2.0 to 6.3.0:
gcc-6.3.0_riscv.patch is a diff between 5fcb8c4 and 173684b in
riscv-gcc, and it needs gcc-6.3.0_memmodel.patch.

- Binutils goes from 2.26.1 to 2.28:
There is a build error for MIPS gold so I add patch for it.

- GMP gets a bump from 6.1.0 to 6.1.2
- MPFR is updated from 3.1.4 to 3.1.5
- GDB is upgraded from 6.1.1 to 6.1.2
- IASL is changed from 20160831 to 20161222
- LLVM is changed from 3.8.0 to 3.9.1

Change-Id: I20fea838d798c430d8c4d2cc6b07614d967c60c5
Signed-off-by: Iru Cai <mytbk920423@gmail.com>
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/17189
Tested-by: build bot (Jenkins)

util/crossgcc/patches/gdb-7.12_pythonhome.patch

@@ -0,0 +1,19 @@
+diff -urN gdb-7.12.orig/gdb/python/python.c gdb-7.12/gdb/python/python.c
+--- gdb-7.12.orig/gdb/python/python.c	2016-02-09 19:19:39.000000000 -0800
++++ gdb-7.12/gdb/python/python.c	2016-04-21 17:45:39.119833428 -0700
+@@ -1748,6 +1748,15 @@
+ #endif
+ #endif
+ 
++  char readlinkbuffer[BUFSIZ];
++  int readlinks = readlink("/proc/self/exe", readlinkbuffer, BUFSIZ - 1);
++  readlinkbuffer[readlinks] = 0;
++  char *executeablepath = dirname(readlinkbuffer);
++  char *pythonhome = malloc(strlen(executeablepath) + strlen("/../") + 2);
++  strcpy(pythonhome, executeablepath);
++  strcat(pythonhome, "/../");
++  setenv("PYTHONHOME", pythonhome, 1);
++
+   Py_Initialize ();
+   PyEval_InitThreads ();
+