libui/libgui: Fix errors in parceling

BufferItem and GraphicBuffer were not parceling correctly, which had
not been noticed because the libgui tests (specifically, one that
tests placing a BufferQueue in a separate process from the IGBP/C)
had not been run recently. This change fixes the errors found in
those classes.

Change-Id: Ie224361a534a79115a3481d83ff97f21d154d4f5
diff --git a/libs/ui/GraphicBuffer.cpp b/libs/ui/GraphicBuffer.cpp
index 638ac62..52fa0df 100644
--- a/libs/ui/GraphicBuffer.cpp
+++ b/libs/ui/GraphicBuffer.cpp
@@ -303,7 +303,7 @@
                 static_cast<size_t>(handle->numInts) * sizeof(int));
     }
 
-    buffer = reinterpret_cast<void*>(static_cast<int*>(buffer) + sizeNeeded);
+    buffer = static_cast<void*>(static_cast<uint8_t*>(buffer) + sizeNeeded);
     size -= sizeNeeded;
     if (handle) {
         fds += handle->numFds;
@@ -385,7 +385,7 @@
         }
     }
 
-    buffer = reinterpret_cast<void const*>(static_cast<int const*>(buffer) + sizeNeeded);
+    buffer = static_cast<void const*>(static_cast<uint8_t const*>(buffer) + sizeNeeded);
     size -= sizeNeeded;
     fds += numFds;
     count -= numFds;