Remove creation of intermediate tuple in makekey.  

Requires copying tuplehash from tupleobject.c.  Improves benchmarks 

* on master
```
Test Suite 2 :

Tests millions of misses and millions of hits to quantify
cache behavior when cache is full.

function call                 speed up
untyped(i, j, a="spammy")         6.68, typed(i, j, a="spammy")           9.37
```

* pr
```
Test Suite 2 :

Tests millions of misses and millions of hits to quantify
cache behavior when cache is full.

function call                 speed up
untyped(i, j, a="spammy")         7.43, typed(i, j, a="spammy")          10.70
```