TextFileTestCase: test for correct parsing of empty Mac lines.

(This is failing both with and without r75387.)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@75797 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
TextFileTestCase: test for \r\r\r\n parsing.

While r75387 fixed parsing of \r\r\n, it still didn't handle triple-\r correctly.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@75798 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Rewrite wxTextFile's newlines parsing to fix multiple bugs.

Remove the complicated parsing state machine that contained bugs with
unexpected inputs and was very hard to modify correctly.  Replace it
with much simpler code that looks ahead, instead of deducing line
endings from past characters.

The new code never looses lines with data and calls AddLine() on the
first newline character it encounters, peeking ahead to determine the
line ending type.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@75799 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Add line-endings fuzzing test to TextFileTestCase.

Stress-test wxTextFile's handling of unusual CR,LF characters.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@75800 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775