Restore entity (d/en)coding for ANSI documents

Since this project came under new maintenance, the
focus has been on the stability of x64 releases

Back in v1.1, the (d/en)coding procedures queried
the document's code page before every transformation.
This was implemented by a pair of complementary
overloaded functions

Each function made a call to WideCharToMultiByte or
MultiByteToWideChar, as appropriate. This became the
source of access violations in 64-bit Notepad++,
sometime after 7.7 was released:

- https://fossil.2of4.net/npp_htmltag/tktview?name=c3c733e21f
- https://community.notepad-plus-plus.org/topic/18488/htmltag-1-1-plugin-broken-since-npp-7-7

087872a resolved that issue -- at the cost of properly
encoding multi-byte text. Preventing a crash was the
only priority at the time, as v1.1 had been rendered
completely unusable in 64-bit editors by a breaking
change to the upstream ABI:

- https://sourceforge.net/p/npp-plugins/discussion/725650/thread/08c8e87447

d2189a1 made another quick fix, one that preferred
Unicode at the expense of ANSI: #3

This makes the encoding of text selections depend on
the document's code page, the way it did before v1.2

Author: Robert Di Pardo

src/LibNppPlugin/NppSimpleObjects.pas

@@ -391,7 +391,12 @@ procedure TTextRange.SetText(const AValue: WideString);
   Chars: AnsiString;
   TxtRng: Integer;
 begin
-  Chars := UTF8Encode(AValue);
+  case FEditor.SendMessage(SCI_GETCODEPAGE) of
+  SC_CP_UTF8:
+    Chars := UTF8Encode(AValue)
+  else
+    Chars := AValue;
+  end;
   TxtRng := System.Length(Chars);
   FEditor.SendMessage(SCI_SETTARGETSTART, FStartPos);
   FEditor.SendMessage(SCI_SETTARGETEND, FEndPos);
@@ -568,7 +573,12 @@ function TSelection.GetText: WideString;
 begin
   Chars := AnsiString(StringOfChar(#0, Self.GetLength + 1));
   FEditor.SendMessage(SCI_GETSELTEXT, 0, PAnsiChar(Chars));
-  Result := WideString(UTF8Decode(Chars));
+  case FEditor.SendMessage(SCI_GETCODEPAGE) of
+    SC_CP_UTF8:
+      Result := WideString(UTF8Decode(Chars))
+    else
+      Result := WideString(UTF8Encode(Chars))
+  end;
 end;
 { ------------------------------------------------------------------------------------------------ }
 procedure TSelection.SetText(const AValue: WideString);
@@ -577,7 +587,12 @@ procedure TSelection.SetText(const AValue: WideString);
   NewLength, EndPos: Sci_Position;
   Reversed: boolean;
 begin
-  Chars := UTF8Encode(AValue);
+  case FEditor.SendMessage(SCI_GETCODEPAGE) of
+  SC_CP_UTF8:
+    Chars := UTF8Encode(AValue)
+  else
+    Chars := AValue;
+  end;
   NewLength := System.Length(Chars) - 1;
   Reversed := (Self.Anchor > Self.GetCurrentPos);
   FEditor.SendMessage(SCI_REPLACESEL, 0, PAnsiChar(Chars));