Regressions on trunk at revision 173307 vs revision 173286

[H.J. Lu Intel64 Core 2/i7]

New failures:
FAIL: gcc.dg/guality/vla-1.c  -O2 -flto  line 17 sizeof (a) == 6

New passes:
FAIL: gcc.target/i386/pr48723.c (internal compiler error)
FAIL: gcc.target/i386/pr48723.c (test for excess errors)