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
diff --git a/driver/rsdSampler.cpp b/driver/rsdSampler.cpp
index 28b594f..8436437 100644
--- a/driver/rsdSampler.cpp
+++ b/driver/rsdSampler.cpp
@@ -29,9 +29,9 @@
 #include <GLES/glext.h>
 #endif
 
-using namespace android;
-using namespace android::renderscript;
-
+using android::renderscript::Context;
+using android::renderscript::Sampler;
+using android::renderscript::rs_sampler;
 
 bool rsdSamplerInit(const Context *, const Sampler *s) {
     return true;