The prototypes for handle parsers needed to be changes because it turned
out "single" was inappropriate for handles as "single" allocates memory
for the parsed object, but handles must be written directly.
The way I wound up using the field meant that exprctx should not "own"
the hashlinks chain, but rather just point to it. This fixes the nasty
access errors I had.
Dependencies on vkparse.hinc were spreading through the code which I
didn't want as that removes a lot of the automation from the automake
files. This keeps all parser code internal to vkparse.c's scope, and any
accesses required for enum and struct (not yet) definitions can be
fetched by name.
Nothing is actually done yet other than parsing the built-in property
list to property list items (the actual parser is just a skeleton), but
everything compiles
