Revert 374450 "Fix __builtin_assume_aligned with too large values."

Revert 374450 "Fix __builtin_assume_aligned with too large values."

The test fails on Windows, with

  error: 'warning' diagnostics expected but not seen:
    File builtin-assume-aligned.c Line 62: requested alignment
        must be 268435456 bytes or smaller; assumption ignored
  error: 'warning' diagnostics seen but not expected:
    File builtin-assume-aligned.c Line 62: requested alignment
        must be 8192 bytes or smaller; assumption ignored

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@374456 91177308-0d34-0410-b5e6-96231b3b80d8