Change the size of the hash table used to cache IP -> debuginfo to a prime nr

This change is based on rumours/legends/oral transmission of experience/...
that prime nrs are good to use for hash table size :).

If someone has a (short) explanation about why this is useful, 
that will be welcome.



git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13237 a5019735-40e9-0310-863c-91ae7b9d1cf9
Implement a more efficient allocation of small blocks which are never freed.
This generalises the "perm_malloc" function which was in ms_main.c
The new VG_(perm_malloc) is used in ms_main.c
and for execontext : when there are a lot of execontext, this
can save significant memory.



git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13238 a5019735-40e9-0310-863c-91ae7b9d1cf9
Add an implementation of memset() that costs half as much on 64 bit
platforms.  (But why are we intercepting memset anyway?  It makes no
sense to me.)


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13239 a5019735-40e9-0310-863c-91ae7b9d1cf9
Import from memcheck land, a less ludicrously inefficient
implementation of memcpy, which copies words at a time rather than
just bytes.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13240 a5019735-40e9-0310-863c-91ae7b9d1cf9