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 23bb3b915c5c7a389ce184e76a989bba94a2495a..a8e0352196abdf4a7eb330ce4a67816d18fd6795 100644
--- a/src/runtime/runtime.h
+++ b/src/runtime/runtime.h
@@ -259,7 +259,10 @@ 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