Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Remove the use of toupper() from rtld_printf.c. Use of the libc function
relies on working TLS, which is particulary not true for LD_DEBUG uses.

MFC after: 1 week

Do not use the function pointers for the internal operation of rtld_printf()
functions. The _rtld_error() function might be called early during the rtld
bootstrap, in which case function pointers are not yet functional on ia64
due to required relocations not yet performed.

Reported, reviewed and tested by: marcel
Approved by: re (bz)

Rtld links with the specially built pic static libc library to get some
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)