posix: Fix mmap for m68k and ia64 (BZ#21908)

posix: Fix mmap for m68k and ia64 (BZ#21908)

Default semantic for mmap2 syscall is to take the offset in 4096-byte
units.  However m68k and ia64 mmap2 implementation take in the
configured pageunit units and for both architecture it can be
different values.

This patch fixes the m68k runtime discover of mmap2 offset unit
and adds the ia64 definition to find it at runtime.

Checked the basic tst-mmap and tst-mmap-offset on m68k (the system
is configured with 4k, so current code is already passing on this
system) and a sanity check on x86_64-linux-gnu (which should not be
affected by this change).  Sergei also states that ia64 loader now
work correctly with this change.

	Adhemerval Zanella  <adhemerval.zanella@linaro.org>
	Sergei Trofimovich  <slyfox@inbox.ru>

	* sysdeps/unix/sysv/linux/m68k/mmap_internal.h (MMAP2_PAGE_SHIFT):
	Rename to MMAP2_PAGE_UNIT.
	* sysdeps/unix/sysv/linux/mmap.c: Include mmap_internal iff
	__OFF_T_MATCHES_OFF64_T is not defined.
	* sysdeps/unix/sysv/linux/mmap_internal.h (page_unit): Declare as
	uint64_t.
	(MMAP2_PAGE_UNIT) [MMAP2_PAGE_UNIT == -1]: Redefine to page_unit.
	(page_unit) [MMAP2_PAGE_UNIT != -1]: Remove definition.