[ion] Namespace Ion::UTF8Helper and Ion::UTF8Decoder

ion/src/shared/unicode/utf8_decoder.cpp

@@ -1,6 +1,8 @@
 #include <ion/unicode/utf8_decoder.h>
 #include <assert.h>
 
+namespace Ion {
+
 static inline int leading_ones(uint8_t value) {
   for (int i=0; i<8; i++) {
     if (!(value & 0x80)) {
@@ -107,3 +109,5 @@ size_t UTF8Decoder::CodePointToChars(CodePoint c, char * buffer, size_t bufferSi
   assert(i == charCount);
   return charCount;
 }
+
+}