add non-ASCII ANSI support; fix GetCurLine bug

FIX: As mentioned in this forum post (https://community.notepad-plus-plus.org/post/102725),
        this plugin pack was previously assuming that Notepad++ internally represented every document as UTF-8,
        regardless of the encoding of that document on the hard drive.
    This assumption appears to have been correct for every document encoding EXCEPT ANSI,
        which meant that non-ASCII text in ANSI documents would previously be garbled by this plugin.
        This issue has now been fixed.

FIX: I *believe* that issue #16 has now been resolved,
    by adding a new parameter to GetNullStrippedStringFromMessageThatReturnsLength.

ADD: Add a new popup notification when changing the lexer language
    for "new 1"-type buffers whose names begin with "lexer test CSharpPluginPack".
    This notification mostly exists to verify that the fixes for both of the above bugs actually work.

Author: molsonkiko

CHANGELOG.md

@@ -34,6 +34,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 7. When building plugin, automatically sync `plugins/yourPluginName/testfiles` folder in your Notepad++ installation with the `testfiles` folder in this repo. Fix [issue #12](https://github.com/molsonkiko/NppCSharpPluginPack/issues/12).
 8. Toggle highlighting of `close HTML/XML tag` toolbar icon based on whether the setting is true.
 9. Toolbar icon hover text is now translated to other languages. Fix [issue #14](https://github.com/molsonkiko/NppCSharpPluginPack/issues/14).
+10. Added support for ANSI-encoded documents containing non-ASCII text. Previously, if a document was ANSI encoded, and the plugin asked for some text from the document, Notepad++ would send ANSI-encoded text and the plugin would attempt to decode it as UTF-8.
 
 ### Fixed
 

NppCSharpPluginPack/Main.cs

@@ -203,7 +203,15 @@ public static void OnNotification(ScNotification notification)
                 modsSinceBufferOpened = 0;
                 return;
             // when the lexer language changed, re-check whether this is a document where we close HTML tags.
+            // also display some text from the document and info about the current lexer if the name of the current file starts with "lexer test CSharpPluginPack".
             case (uint)NppMsg.NPPN_LANGCHANGED:
+                if (Npp.notepad.GetCurrentFilePath().StartsWith("lexer test CSharpPluginPack"))
+                {
+                    MessageBox.Show($"The current line's text is {Npp.editor.GetCurLine().TrimEnd(new char[] {'\r', '\n'})}.\r\n" +
+                                    (Npp.editor.GetNamedStyles() < 2 ? "There are fewer than two named styles for this lexer.\r\n" : $"The first two named styles for this lexer are {Npp.editor.NameOfStyle(0)} and {Npp.editor.NameOfStyle(1)}.\r\n") +
+                                    "This notification appeared because the lexer language just changed and the name of the current file starts with \"lexer test CSharpPluginPack\"",
+                                    "CSharpPluginPack notification when lexer language is changed");
+                }
                 DoesCurrentLexerSupportCloseHtmlTag();
                 break;
             // when closing a file