Fix: Memory leak in ICUParagraphLayout::NextLine() (#11895)

This function calls icu::BreakIterator::createLineInstance() but does not clean up after it.

Instead use a static instance that is cloned (for thread-safety) and deleted as necessary.

src/gfx_layout.cpp

@@ -334,6 +334,16 @@ Font *Layouter::GetFont(FontSize size, TextColour colour)
 	return fonts[size][colour].get();
 }
 
+/**
+ * Perform initialization of layout engine.
+ */
+void Layouter::Initialize()
+{
+#if defined(WITH_ICU_I18N) && defined(WITH_HARFBUZZ)
+	ICUParagraphLayoutFactory::InitializeLayouter();
+#endif /* WITH_ICU_I18N && WITH_HARFBUZZ */
+}
+
 /**
  * Reset cached font information.
  * @param size Font size to reset.