fix 'g:NERDAllowAnyVisualDelims' behavior

[jiaobuzuji]

Hi Maintainer

I found that the behavior of the 'g:NERDAllowAnyVisualDelims' option is inconsistent with that described in the document.

nerdcommenter/doc/nerdcommenter.txt

Lines 524 to 545 in 2c87cae

	*'NERDAllowAnyVisualDelims'*
	Values: 0 or 1.
	Default: 1.
	If set to 1 then, when doing a visual or visual-block comment (but not a
	visual-line comment), the script will choose the right delimiters to use for
	the comment. This means either using the current delimiters if they are
	multipart or using the alternative delimiters if THEY are multipart. For
	example if we are editing the following java code: >
	float foo = 1221;
	float bar = 324;
	System.out.println(foo * bar);
	<
	If we are using // comments and select the "foo" and "bar" in visual-block
	mode, as shown left below (where '|'s are used to represent the visual-block
	boundary), and comment it then the script will use the alternative delimiters
	as shown on the right: >
	float |foo| = 1221; float /*foo*/ = 1221;
	float |bar| = 324; float /*bar*/ = 324;
	System.out.println(foo * bar); System.out.println(foo * bar);
	<

PR #440 .

Best Respect.

[alerque]

Thanks for taking the time to contribute. I had to read tho code about 5 times before the logic made sense but I think this change is correct. Since I don't actually use the feature much I have to wonder if we'll take anybody by surprised based on what the code did instead of how it was documented. I guess we'll see.