ruby.h: relax rb_funcall check on extra args for clang

	clang 5.+ (tested clang 7.0.0) seems to be attempting division-by-zero
	and giving a very large number for static args to rb_funcall.

	* include/ruby/ruby.h (rb_varargs_bad_length): relax check for clang
	* ext/-test-/funcall/funcall.c: renamed from passing_block.c
	  define extra_args_name function
	* test/-ext-/funcall/test_funcall.rb: new test
	  [ruby-core:85266] [Bug #14425]

	From: Eric Wong <e@80x24.org>

	ruby.h: relax rb_funcall(obj, id, 0, 0) case only

	* include/ruby/ruby.h (rb_varargs_argc_valid_p): relax rb_funcall
	  check on extra args only if argc == 0, for the compatibility
	  with wrong code which is probably confused with rb_funcallv.
	  [Bug #14425]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_5@62501 b2dd03c8-39d4-4d8f-98ff-823fe69b080e