line-break in wikilink is handled incorrectly

[CXuesong]

Currently, the Text part of WIKILINK cannot contain line-break. E.g.

[[Test|abc
def]]

However, this is a valid wikilink expression.

For now, the expression above is parsed as

Wikitext             [[[Test|abc\r\ndef]]\r\n]
.Paragraph           [[[Test|abc\r\ndef]]\r\n]
..PlainText          [[[Test|abc\r\ndef]]\r\n]