[Sanitizer] Minor enhancements in InternalVector container

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@178238 91177308-0d34-0410-b5e6-96231b3b80d8
[ASan] Speed-up initialization-order checking: create and use fast versions of PoisonShadow functions, store copies of __asan_global descriptors in a vector instead of list of pointers. This gives 3x speedup on both benchmarks and real binaries with lots of globals.

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@178239 91177308-0d34-0410-b5e6-96231b3b80d8