Aligning native Parcel implementation to Java.

The Java implementation of writing the RPC response header
calculates the length of the header including the 4 bytes
specifying the header length but the native implementation
excludes the 4 bytes specifying the length from the header
length.
The native implementation has been aligned to the Java impl.

Change-Id: I325bf272a63152d8fded4cf4e51a906b5a9bfe19

Author: Magnus Strandberg

libs/binder/Parcel.cpp

@@ -1047,10 +1047,11 @@ int32_t Parcel::readExceptionCode() const
 {
   int32_t exception_code = readAligned<int32_t>();
   if (exception_code == EX_HAS_REPLY_HEADER) {
+    int32_t header_start = dataPosition();
     int32_t header_size = readAligned<int32_t>();
     // Skip over fat responses headers.  Not used (or propagated) in
     // native code
-    setDataPosition(dataPosition() + header_size);
+    setDataPosition(header_start + header_size);
     // And fat response headers are currently only used when there are no
     // exceptions, so return no error:
     return 0;