Allow GLFW_INVALID_VALUE at Init

[hajimehoshi]

Closes #324
Updates #292

[hajimehoshi]

PTAL

[dmitshur]

LGTM. There's a typo in the commit message/PR subject, s/GLFW_INVLAID_VALUE /GLFW_INVALID_VALUE/.

[dmitshur]

Thinking about this more (sorry I missed it earlier), this workaround should probably not return invalidValue from Init, but rather handle it internally.

That is, most callers of glfw.Init look like this:

err := glfw.Init()
if err != nil {
    log.Fatalln("glfw.Init failed:", err)
}

This temporary workaround shouldn't require users to also temporarily update their code.

Perhaps something like:

err := acceptError(APIUnavailable, invalidValue)
if e, ok := err.(*Error); ok && e.Code == invalidValue {
    // This is an internal and non-fatal error that's being intentionally ignored.
    err = nil
}
return err

(It's also possible to handle it by logging, but given GLFW 3.3.5 outright removes it, logging doesn't seem to be needed.)