Revert "Fold dangling-field warning into general initialization lifetime checks."

This reverts commit r337627.
After the change, clang started producing invalid warning on the following code:
    struct foo {
      foo(char *x) : x_(&x[10]) {}
    private:
      char *x_;
    };

1.cpp:2:21: warning: initializing pointer member 'x_' with the stack address of parameter 'x' [-Wdangling-field]

llvm-svn: 337671