elf/dl-load.c: Use __strdup.

During a refactoring pass several repeated blocks of code in dl-load.c
were turned into a call to a local function named local_strdup.  There
is no need for local_strdup, and the routines should instead call
__strdup.  This change does just that.  We call the internal symbol
__strdup because calling strdup is unsafe.  The user might be
using a standard that doesn't include strdup and may have defined this
symbol in their application. During a static link we might reference
the user defined symbol and crash if it doesn't implement a standards
conforming strdup. The resulting code is simpler to understand, and
makes it easier to debug.

No regressions on x86_64.

2014-10-28  Carlos O'Donell  <carlos@redhat.com>

	* dl-load.c (local_strdup): Remove.
	(expand_dynamic_string_token): Use __strdup.
	(decompose_rpath): Likewise.
	(_dl_map_object): Likewise.
manual/llio.texi: Add Linux-specific comments for write().

Add Linux-specific comments about the atomicity of write() and
the POSIX requirements.

2014-10-29  Carlos O'Donell  <carlos@redhat.com>

	* manual/llio.texi: Add comments discussing why write() may be
	considered MT-unsafe on Linux.