type inference for templating

[danielkeller]

add argstype

in anytype, add bool "needed."
DoFunc on function even if args are abstract
when stepping thru a function, mark "problem" anytypes as needed.
when checking func cadidates, make sure all needed anys are filled
when merging (? add new function?) don't merge unneeded anys
this fixes the "do i merge refs" problem, and lets us do list ops in vec as opposed to c
however: some list ops need element size, which is ok if the compiler can insert it but not ok if its a user function call

func is template if args contain "needed" anys

do we still need merge?

add function type!