Bump MoarVM and add new nqp::codes op

Gets the number of codepoints in the string.

Changes brought in by MoarVM bump:
abc38137 Fix MVM_string_compare to support deterministic comparing of synthetics
b161c851 be safe about marking NULL call graph nodes
1d3a139b Avoid range check on every SC object access.
5c67d732 calloc a tospace instead of memset old fromspace.
2bfee713 Break MVM_sc_get_sc into inline and slow path.
1db5c502 No longer force static frame into gen2 after spesh
eff1b1f3 Fix typo; MasterDuke17++.
7fae17c9 Move spesh stats to spesh object.
5fdfddf3 Move spesh arg guards into spesh object.
838f7cf7 Move candidates and entries count to spesh object.
3f26aa9a Add spesh data REPR; hang off static frame.

tools/build/MOAR_REVISION

@@ -1 +1 @@
-2017.07-253-g82c282e
+2017.07-264-gabc38137