rtld: Shrink by eliminating stdio

rtld: Shrink by eliminating stdio

Eliminate stdio for parsing libmap.conf, and instead parse it from direct
mapping.  Also stop using strerror(3) in rtld which sucks in msgcat and
stdio.  Instead directly access sys_errlist array of error messages with
private rtld_strerror() function.

Results on x86_64 (includes debug symbols):

> size /usr/libexec/ld-elf.so.2*
   text	   data	    bss	    dec	    hex	filename
  95294    1560    7680  104534   19856 /usr/libexec/ld-elf.so.2
 108830    3128   18216  130174   1fc7e /usr/libexec/ld-elf.so.2.old

> ls -al /usr/libexec/ld-elf.so.2*
-r-xr-xr-x  1 root  wheel  305763 Mar 16 20:33 /usr/libexec/ld-elf.so.2
-r-xr-xr-x  1 root  wheel  370392 Mar 14 00:02 /usr/libexec/ld-elf.so.2.old

Taken from:
FreeBSD SVN 232862 (2012-03-12)
FreeBSD SVN 232974 (2012-03-14)