posix: Fix large mmap64 offset for mips64n32 (BZ#24699)

posix: Fix large mmap64 offset for mips64n32 (BZ#24699)

The fix for BZ#21270 (commit 158d5fa0e19) added a mask to avoid offset larger
than 1^44 to be used along __NR_mmap2.  However mips64n32 users __NR_mmap,
as mips64n64, but still defines off_t as old non-LFS type (other ILP32, such
x32, defines off_t being equal to off64_t).  This leads to use the same
mask meant only for __NR_mmap2 call for __NR_mmap, thus limiting the maximum
offset it can use with mmap64.

This patch fixes by setting the high mask only for __NR_mmap2 usage. The
posix/tst-mmap-offset.c already tests it and also fails for mips64n32. The
patch also change the test to check for an arch-specific header that defines
the maximum supported offset.

Checked on x86_64-linux-gnu, i686-linux-gnu, and I also tests tst-mmap-offset
on qemu simulated mips64 with kernel 3.2.0 kernel for both mips-linux-gnu and
mips64-n32-linux-gnu.

	[BZ #24699]
	* posix/tst-mmap-offset.c: Mention BZ #24699.
	(do_test_bz21270): Rename to do_test_large_offset and use
	mmap64_maximum_offset to check for maximum expected offset value.
	* sysdeps/generic/mmap_info.h: New file.
	* sysdeps/unix/sysv/linux/mips/mmap_info.h: Likewise.
	* sysdeps/unix/sysv/linux/mmap64.c (MMAP_OFF_HIGH_MASK): Define iff
	__NR_mmap2 is used.