[Issue 21371] New: core.stdcpp.allocator: _Adjust_manually_vector_aligned checks for sentinel unconditionally (Windows only)

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=21371

          Issue ID: 21371
           Summary: core.stdcpp.allocator: _Adjust_manually_vector_aligned
                    checks for sentinel unconditionally (Windows only)
           Product: D
           Version: D2
          Hardware: All
                OS: Windows
            Status: NEW
          Severity: normal
          Priority: P1
         Component: druntime
          Assignee: nobody at puremagic.com
          Reporter: n8sh.secondary at hotmail.com

This bug resulted in assertion failures when deleting large blocks of memory
using core.stdcpp.allocator on Microsoft Windows.
_Allocate_manually_vector_aligned sets a sentinel when version(_DEBUG).
_Adjust_manually_vector_aligned checks for this sentinel when assertions are
enabled without checking version(_DEBUG).

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