Limit appending of ShortStrings to Ropes to string length < 30

The larger the size of ShortStrings we allow to be appended directly to
Ropes, the more memory Wattsi consumes at runtime.

We don’t need the size to be anywhere near as big as 255 — the existing
code never actually needs to directly append strings with lengths any
longer than 30. If we ever do run into need to append string lengths
longer than 30, we could at that time just bump UTF8InlineSize up to
whatever new size we actually need.

Upping the size to 30 from the old size of 15 seems to increase the
memory consumption by about 15–20%, or around 80–100MB. (In comparison,
upping it to 255 seems to roughly double the memory consumption.)

src/lib/ropes.pas

@@ -41,14 +41,14 @@       TFixedSizeRopeFragment = record
     private
      const
       FragmentPayloadSize = SizeOf(TFixedSizeRopeFragment);
-      UTF8InlineSize = 255;
+      UTF8InlineSize = 30;
       CodepointsSize = (FragmentPayloadSize-SizeOf(Byte)) div SizeOf(TUnicodeCodepoint);
      type
       TUTF8InlineIndex = 0..UTF8InlineSize-1;
       TUTF8InlineIndexPlusOne = 0..UTF8InlineSize;
       TCodepointsIndex = 0..CodepointsSize-1;
       TCodepointsIndexPlusOne = 0..CodepointsSize;
-      TInlineString = String[UTF8InlineSize];
+      TInlineString = String[UTF8InlineSize + 1];
       PRopeFragment = ^TRopeFragment;
       TRopeFragment = record
          Next: PRopeFragment;
@@ -963,6 +963,11 @@ procedure Rope.Append(const NewString: RopeInternals.TInlineString);
    {$IFDEF VERBOSE} if (DebugNow) then Writeln('Ropes: Append(ShortString) on rope @', IntToHex(PtrUInt(@Self), 16), ' with data @', IntToHex(PtrUInt(FValue), 16)); {$ENDIF}
    {$IFDEF VERBOSE} if (DebugNow) then Writeln('Ropes:   Length(FValue)=', Length(FValue)); {$ENDIF}
    Assert(Length(NewString) <= RopeInternals.UTF8InlineSize, 'Maximum size of short string is ' + IntToStr(RopeInternals.UTF8InlineSize));
+   if (Length(NewString) > RopeInternals.UTF8InlineSize) then
+   begin
+      Writeln('Error: Operation attempted with string length > UTF8InlineSize: "' + NewString + '..."');
+      Halt(1);
+   end;
    if ((not Assigned(FLast)) or (FLast^.Kind <> rfUTF8Inline) or (RopeInternals.UTF8InlineSize - FLast^.InlineLength < Length(NewString))) then
    begin
       EnsureSize(1, 1);