Fix more system/core/include warnings

The warnings in these files were hidden by -isystem
framework/native/include.

Bug: 31752268
Test: m -j
Change-Id: I2a54376aea380ee24e6483fb7d35fdfe8991c490
diff --git a/include/utils/Flattenable.h b/include/utils/Flattenable.h
index c37ac60..22b811a 100644
--- a/include/utils/Flattenable.h
+++ b/include/utils/Flattenable.h
@@ -31,32 +31,32 @@
 
 class FlattenableUtils {
 public:
-    template<int N>
+    template<size_t N>
     static size_t align(size_t size) {
         COMPILE_TIME_ASSERT_FUNCTION_SCOPE( !(N & (N-1)) );
         return (size + (N-1)) & ~(N-1);
     }
 
-    template<int N>
+    template<size_t N>
     static size_t align(void const*& buffer) {
         COMPILE_TIME_ASSERT_FUNCTION_SCOPE( !(N & (N-1)) );
-        intptr_t b = intptr_t(buffer);
-        buffer = (void*)((intptr_t(buffer) + (N-1)) & ~(N-1));
-        return size_t(intptr_t(buffer) - b);
+        uintptr_t b = uintptr_t(buffer);
+        buffer = reinterpret_cast<void*>((uintptr_t(buffer) + (N-1)) & ~(N-1));
+        return size_t(uintptr_t(buffer) - b);
     }
 
-    template<int N>
+    template<size_t N>
     static size_t align(void*& buffer) {
         return align<N>( const_cast<void const*&>(buffer) );
     }
 
     static void advance(void*& buffer, size_t& size, size_t offset) {
-        buffer = reinterpret_cast<void*>( intptr_t(buffer) + offset );
+        buffer = reinterpret_cast<void*>( uintptr_t(buffer) + offset );
         size -= offset;
     }
 
     static void advance(void const*& buffer, size_t& size, size_t offset) {
-        buffer = reinterpret_cast<void const*>( intptr_t(buffer) + offset );
+        buffer = reinterpret_cast<void const*>( uintptr_t(buffer) + offset );
         size -= offset;
     }