No functional change.

first calls mmap() with the arguments PROT_NONE and MAP_ANON to reserve a
single, contiguous range of virtual addresses for the entire shared library.
Later, rtld calls mmap() with the the shared library's file descriptor
and the argument MAP_FIXED to place the text and data sections within the
reserved range.  The rationale for mapping shared libraries in this way is
explained in the commit message for Revision 190885.  However, this approach
does have an unintended, negative consequence.  Since the first call to
mmap() specifies MAP_ANON and not the shared library's file descriptor, the
kernel has no idea what alignment the vm object backing the file prefers.
As a result, the reserved range's alignment is unlikely to be the same as
the vm object's, and so mapping with superpages becomes impossible.  To
address this problem, this revision adds the argument MAP_ALIGNED_SUPER to
the first call to mmap() if the text section is larger than the smallest
superpage size.

To determine if the text section is larger than the smallest superpage
size, rtld must always fetch the page size information.  As a result, the
private code for fetching the base page size in rtld's builtin malloc is
redundant.  Eliminate it.  Requested by: kib

Tested by:	zbb (on arm)
Reviewed by:	kib (an earlier version)
Discussed with:	jhb

permitted by the University of Berkeley on July 22, 1999.

Reviewed by:	imp
MFC after:	1 week

malloc hardly would ever be updated.

Reviewed by:  bde, kan
MFC after:    2 weeks

C runtime services, like printf(). Unfortunately, the multithread-safeness
measures in the libc do not work in rtld environment.

Rip the kernel printf() implementation and use it in the rtld instead of
libc version. This printf does not require any shared global data and thus
is mt-safe. Systematically use rtld_printf() and related functions, remove
the calls to err(3).

Note that stdio is still pulled from libc due to libmap implementaion using
fopen(). This is safe but unoptimal, and can be changed later.

Reported and tested by:	pgj
Diagnosed and reviewed by:	kan (previous version)
Approved by:	re (bz)

Use local version of getpagesize(), rtld_getpagesize() in private allocator.
Override the __getosreldate() previously fetched from libc_pic.a with
local version that uses aux value if present. Note that __getosreldate()
is used by rtld indirectly, by mmap(2) libc wrapper.

To be able to utilize aux, split digest_dynamic() for use by init_rtld()
into two parts, where the first one does not call malloc(), and the
second part uses it. init_rtld() is able to initialize global variables
before digest_dynamic2() calls. In particular, pagesize and osreldate are
set up from the aux values.

Now, rtld avoids (two) sysctl calls in startup.

Tested by:	marius (sparc64)
MFC after:	1 month

  * Add posix_memalign().

  * Move calloc() from calloc.c to malloc.c.  Add a calloc() implementation in
    rtld-elf in order to make the loader happy (even though calloc() isn't
    used in rtld-elf).

  * Add _malloc_prefork() and _malloc_postfork(), and use them instead of
    directly manipulating __malloc_lock.

Approved by:	phk, markm (mentor)