Fix google-build-using-namespace warnings in driver.

* Replace "using namespace ..." statements with
  using declarations of the required names.
* Put extern "C" functions inside a namespace to save
  a lot of using declarations. Their linkage names are not
  changed but can access names in the namespace easily.

Bug: 32670901
Test: build with WITH_TIDY=1
Change-Id: I7a2d45ecab47bc9064701fd288fe31f47b28fcc9

driver/rsdAllocation.cpp

diff --git a/driver/rsdAllocation.cpp b/driver/rsdAllocation.cpp
index 3816c23..83d4407 100644
--- a/driver/rsdAllocation.cpp
+++ b/driver/rsdAllocation.cpp
@@ -44,8 +44,21 @@
 #include <malloc.h>
 #endif
 
-using namespace android;
-using namespace android::renderscript;
+#ifndef RS_COMPATIBILITY_LIB
+using android::GraphicBufferMapper;
+using android::PIXEL_FORMAT_RGBA_8888;
+using android::Rect;
+#endif
+
+using android::renderscript::Allocation;
+using android::renderscript::Context;
+using android::renderscript::Element;
+using android::renderscript::Type;
+using android::renderscript::rs_allocation;
+using android::renderscript::rsBoxFilter565;
+using android::renderscript::rsBoxFilter8888;
+using android::renderscript::rsMax;
+using android::renderscript::rsRound;
 
 #ifndef RS_COMPATIBILITY_LIB
 const static GLenum gFaceOrder[] = {