Fixed handling of text wrapping and a text layout corner case

Due to using QTextCursor::columnNumber() instead of
QTextCursor::positionInBlock(), a lot of code would not work correctly
when used with wrapped lines.

In addition, there was an issue with columnNumber() returning 0 right
after inserting a character before the last character of a line.

Reviewed-by: mae

src/plugins/qmljseditor/qmljscodecompletion.cpp

@@ -513,7 +513,7 @@ bool CodeCompletion::triggersCompletion(TextEditor::ITextEditable *editor)
 
             QTextCursor tc = ed->textCursor();
             QTextBlock block = tc.block();
-            const int column = tc.columnNumber();
+            const int column = tc.positionInBlock();
             const int blockState = qMax(0, block.previous().userState()) & 0xff;
             const QString blockText = block.text();