Use ICU case conversion/transliterator for case conversion behind a flag

src/runtime/runtime.h

Index: src/runtime/runtime.h
diff --git a/src/runtime/runtime.h b/src/runtime/runtime.h
index 9b62cddfa9ca4a53e2504f3a87c1defa81baa33e..d45a7ef31b72bd115d4e31fa077f25d3d785132f 100644
--- a/src/runtime/runtime.h
+++ b/src/runtime/runtime.h
@@ -264,7 +264,10 @@ namespace internal {
   F(BreakIteratorFirst, 1, 1)                \
   F(BreakIteratorNext, 1, 1)                 \
   F(BreakIteratorCurrent, 1, 1)              \
-  F(BreakIteratorBreakType, 1, 1)
+  F(BreakIteratorBreakType, 1, 1)            \
+  F(StringToLowerCaseI18N, 1, 1)             \
+  F(StringToUpperCaseI18N, 1, 1)             \
+  F(StringLocaleConvertCase, 3, 1)
 #else
 #define FOR_EACH_INTRINSIC_I18N(F)
 #endif