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_5.nim

@@ -0,0 +1,25 @@
+discard """
+cmd: "nim check $file"
+errormsg: "'m' has unspecified generic parameters"
+nimout: '''
+t5167_5.nim(20, 9) Error: 't' has unspecified generic parameters
+t5167_5.nim(21, 5) Error: 't' has unspecified generic parameters
+t5167_5.nim(23, 9) Error: 'm' has unspecified generic parameters
+t5167_5.nim(24, 5) Error: 'm' has unspecified generic parameters
+'''
+"""
+
+template t[B]() =
+  echo "foo1"
+
+macro m[T]: stmt = nil
+
+proc bar(x: proc (x: int)) =
+  echo "bar"
+
+let x = t
+bar t
+
+let y = m
+bar m
+