Avoid GCC 4.6 segfaults

Buildroot's attempt to build a GCC 4.6.x cross-compilation toolchain might fail
with something like

/some/path/buildroot-2013.02/output/toolchain/gcc-4.6.3/libgcc/../gcc/libgcc2.c: In function ‘__negdi2’:
/some/path/buildroot-2013.02/output/toolchain/gcc-4.6.3/libgcc/../gcc/libgcc2.c:72:1: internal compiler error: Segmentation fault

This patch is revision 191605 for GCC 4.7.x
(<https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=191605>).  Applying it
to 4.6.x seems to prevent this crash.

Save this file as
  buildroot-2013.02/toolchain/gcc/4.6.3/999-ira-int.patch
to have buildroot apply this patch to GCC 4.6.x source before trying to build
it.

See also <https://gcc.gnu.org/ml/gcc-help/2014-03/msg00049.html>

Index: buildroot-2013.02/toolchain/gcc/4.6.3/999-ira-int.patch
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ buildroot-2013.02/toolchain/gcc/4.6.3/999-ira-int.patch	2015-03-29 00:09:28.000000000 -0400
@@ -0,0 +1,18 @@
+--- gcc-4_7-branch/gcc/ira-int.h	2012/09/21 09:19:39	191604
++++ gcc-4_7-branch/gcc/ira-int.h	2012/09/21 10:08:35	191605
+@@ -1138,8 +1138,13 @@
+ ira_allocno_object_iter_cond (ira_allocno_object_iterator *i, ira_allocno_t a,
+ 			      ira_object_t *o)
+ {
+-  *o = ALLOCNO_OBJECT (a, i->n);
+-  return i->n++ < ALLOCNO_NUM_OBJECTS (a);
++  int n = i->n++;
++  if (n < ALLOCNO_NUM_OBJECTS (a))
++    {
++      *o = ALLOCNO_OBJECT (a, n);
++      return true;
++    }
++  return false;
+ }
+ 
+ /* Loop over all objects associated with allocno A.  In each