TextDocument.positionAt and offsetAt incorrectly include line endings

[mroch]

The Position docs say that you can't specify a position between an \r and \n, or after a line ending:

vscode-languageserver-node/textDocument/src/main.ts

Lines 19 to 20 in f2ff7d5

	* Positions are line end character agnostic. So you can not specify a position that
	* denotes `\r|\n` or `\n|` where `|` represents the character offset.

And that if the character is too big it defaults to the line length:

vscode-languageserver-node/textDocument/src/main.ts

Lines 40 to 41 in f2ff7d5

	* If the character value is greater than the line length it defaults back
	* to the line length. This property is implementation specific.

But these cases do include the line endings:

const document = newDocument('A\nB\rC\r\nD');
assert.equal(document.offsetAt(Positions.create(0, 10)), 2);
assert.equal(document.offsetAt(Positions.create(1, 10)), 4);
assert.equal(document.offsetAt(Positions.create(2, 2)), 6); // between \r and \n
assert.equal(document.offsetAt(Positions.create(2, 3)), 7);
assert.equal(document.offsetAt(Positions.create(2, 10)), 7);
assert.equal(document.offsetAt(Positions.create(3, 10)), 8);

// this should be (2, 1), I think
assert.deepEqual(document.positionAt(6), Positions.create(2, 2)); // between \r and \n

I think the line length of each line is 1, so the invalid positions should be treated as (line, 1), and the correct offsets should be 1, 3, 5, 5, 5, 8 respectively

[dbaeumer]

@aeschli since you are back from vacation can you please have a look since you originally wrote the code. There is also a PR with test cases.