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_1.nim

@@ -0,0 +1,17 @@
+discard """
+errormsg: "'bar' doesn't have a concrete type, due to unspecified generic parameters."
+line: 16
+"""
+
+proc foo[T]() =
+  var y1 = foo[string]
+  var y2 = foo[T]
+
+proc bar[T]() =
+  let x = 0
+
+let good1 = foo[int]
+let good2 = bar[int]
+
+let err = bar
+