* Split out HEK size calculation into hek_size(). Add the shared HE overhead.
* Handle shared hash key scalars correctly.
* GvNAME() is shared from 5.10 onwards.
+ * Count HvNAME(), the HV "aux" struct, the mro_meta struct, and ENAMEs.
0.76 2011-05-11 nicholas
* Just fix the version number in the line below.