[ASan] One more fix for realloc: check that reallocated chunk is valid before calling memcpy

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@183390 91177308-0d34-0410-b5e6-96231b3b80d8
[ASan] Add a few tests for use-after-scope mode

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@183391 91177308-0d34-0410-b5e6-96231b3b80d8