libutils: turn on -Werror

- Deal with some -Wunused issues
- Override PRI macros (windows)
- Revert use of PRI macros on off64_t (linux)
- Deal with a gnu++11 complaince issue

Change-Id: Ie66751293bd84477a5a6dfd8a57e700a16e36964
diff --git a/libutils/Unicode.cpp b/libutils/Unicode.cpp
index a66e3bb..fe8887d 100644
--- a/libutils/Unicode.cpp
+++ b/libutils/Unicode.cpp
@@ -576,7 +576,7 @@
 char16_t* utf8_to_utf16_n(const uint8_t* src, size_t srcLen, char16_t* dst, size_t dstLen) {
     const uint8_t* const u8end = src + srcLen;
     const uint8_t* u8cur = src;
-    const uint16_t* const u16end = dst + dstLen;
+    const char16_t* const u16end = dst + dstLen;
     char16_t* u16cur = dst;
 
     while (u8cur < u8end && u16cur < u16end) {