Fix gcc-4.4/fedora 11 by adding a sentinel value to SimpleValueType.

Fix gcc-4.4/fedora 11 by adding a sentinel value to SimpleValueType.

gcc-4.4 was optimizing away comparisons against SimpleValueType when
it was compared to a value larger than the largest value in the enum.
This patch works around it by adding one extra item to the enum so
that these tests will now be valid.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@79401 91177308-0d34-0410-b5e6-96231b3b80d8