Apply golang runtime function signatures from info stored in json api
snapshot files.
The api snapshot files are created by a custom go helper program that
uses the go compiler parser to parse the go toolchain source tree and
writes the discovered function and type info into a json file.
The go-api-parser helper program is based off of work contributed by
github user monoidic via issue #6367.
Updates generic functions to take a generic dictionary RTTI
parameter (mostly to allow correct assignment of other parameters).
Updates closure functions to take a closure context parameter. Closure
contexts are passed via a register that is not involved in normal
parameter passing.
Tweaks the signature of gcWriteBarrier functions so that they don't mess
up decompilation of functions that use them.
