Fixes #5167 and related problems (#5475)

This commit returns to a bit less strict checking of the number
of macro arguments, because some old immediate macros rely on a
behavior where even the arity of the macro is not being checked.

It may be better if such macros are just declared to use varargs[expr],
but this remains for another day.

tests/errmsgs/t5167_2.nim

@@ -0,0 +1,12 @@
+discard """
+cmd: "nim c --threads:on $file"
+errormsg: "'threadFunc' doesn't have a concrete type, due to unspecified generic parameters."
+line: 11
+"""
+
+proc threadFunc[T]() {.thread.} =
+  let x = 0
+
+var thr: Thread[void]
+thr.createThread(threadFunc)
+