Cleanup compile warnings.

2013-12-19  Paul Pluzhnikov  <ppluzhnikov@google.com>

	* elf/dl-misc.c (ptr_to_signal_safe_allocator_header): New function.
	(__signal_safe_memalign, __signal_safe_free): Use it.
	(__signal_safe_realloc): Likewise.
Fix incorrect power of 2 check in last commit.
Fix white space as well.