Missing column index parameter for ListView::column_width()

[nickbeth]

Issue

ListView::column_width() seems to be missing the column index parameter. This in turn makes it always request the width of the first column (index 0), when the underlying API call lets the user choose which column to query.

Relevant Win32 API reference can be found here.

Fix

Add a column_index parameter to ListView::column_width() and pass it as the wParam of the send_message call.