Add probes for malloc retries.

Add probes for malloc retries.

for ChangeLog

	* malloc/malloc.c (__libc_malloc): Add memory_malloc_retry probe.
	(__libc_realloc): Add memory_realloc_retry probe.
	(__libc_memalign): Add memory_memalign_retry probe.
	(__libc_valloc): Add memory_valloc_retry probe.
	(__libc_pvalloc): Add memory_pvalloc_retry probe.
	(__libc_calloc): Add memory_calloc_retry probe.
	* manual/probes.texi: Document them.