mmap on 4k boundaries

[Chris January]

I can't make a patch for this at the moment, but FYI you can map a section
on a 4k page bounday using the AT_ROUND_TO_PAGE flag. So on Windows NT, mmap
should be able to map on a 4k page boundary using this function.

	NTSTATUS Status = ZwMapViewOfSection (handle,			// SectionHandle
							  NtCurrentProcess (),	// ProcessHandle
							  address,			// BaseAddress
							  0L,				// ZeroBits
							  size,   		   	// CommitSize
							  &offset,			// SectionOffset
							  &size,		      // ViewSize
							  ViewShare,            // InheritDispostion,
							  AT_ROUND_TO_PAGE,	// AllocationType
							  PAGE_READWRITE		// Protect
							  );

Prototype:

NTSYSAPI
NTSTATUS
NTAPI
ZwMapViewOfSection(
    IN HANDLE SectionHandle,
    IN HANDLE ProcessHandle,
    IN OUT PVOID *BaseAddress,
    IN ULONG ZeroBits,
    IN ULONG CommitSize,
    IN OUT PLARGE_INTEGER SectionOffset OPTIONAL,
    IN OUT PULONG ViewSize,
    IN SECTION_INHERIT InheritDisposition,
    IN ULONG AllocationType,
    IN ULONG Protect
    );

typedef enum _SECTION_INHERIT {
  ViewShare = 1,
  ViewUnmap = 2
} SECTION_INHERIT;

#define AT_EXTENDABLE_FILE 0x00002000
#define SEC_NO_CHANGE 0x00400000
#define AT_RESERVED 0x20000000
#define AT_ROUND_TO_PAGE 0x40000000