`FuncForPC()` returns function/file/line metadata for any given code
position (effectively a memory address). However, since GopherJS runtime
doesn't have access to raw addresses, we emulate this by assigning
virtual position counters for call places seen by Caller() and use them
to retrieve the original function information.

This is a more limited implementation that the upstream, but I expect it
to work for most of the real-life cases, and it fixes a few test
failures in the `reflect` package. With this it should be fairly easy to
bring back proper support for `testing.T.Helper()` function.

Co-authored-by: Jonathan Hall <flimzy@flimzy.com>

Previously we could return anything that may or may not have matched the
required function signature, causing hard to debug failures in the code.
This change replicates the upstream Go behavior.

In the upstream it is implemented in `runtime` and exported into
`reflect` via a go:linkname directive, but GopherJS doesn't support that
and we already define a local typeOffList in `reflect` as a substitute.

Also delete it from reflectlite, since it isn't actually used there.

Co-authored-by: visualfc <visualfc@gmail.com>

It has been introduced all the way back in Go 1.10, but GopherJS never
properly supported it. The new implementation seems to pass most of the
tests, which is an improvement. There are a couple of tests that are
still failing, but fixing that seems like a harder task.

The code is based on goplusjs/gopherjs@a293d52.

Co-authored-by: visualfc <visualfc@gmail.com>

This reflects a change in the upstream intended to make use of terms
"value" and "element" more consistent in the context of maps.

This commit is based on
goplusjs/gopherjs@f4ae589 and
goplusjs/gopherjs@143d71b.

Co-authored-by: visualvc <visualfc@gmail.com>

The original test was using a signalling NaN, but JavaScript appears to
coerce all NaNs to quiet ones. I found no mention of this behavior in
the spec, but I suspect it is just the behavior JavaScript historically
implemented when dealing with NaNs.

Co-authored-by: Jonathan Hall <flimzy@flimzy.com>

Several `reflect` tests rely on it to execute correctly.

`go generate ./...`