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

* Remove "using namespace ..." statements.
* Replace them with using declarations of the required names.
* Enclose the C++ methods and static and extern "C" functions with
  namespace android and renderscript.
* Keep global C++ functions as-is and add using declarations for them.

Bug: 32670901
Test: build with WITH_TIDY=1
Change-Id: I818de466e8786a6c4f9ce0cd8e0fe027f34d7fad
diff --git a/cpu_ref/rsCpuIntrinsic3DLUT.cpp b/cpu_ref/rsCpuIntrinsic3DLUT.cpp
index add5cd8..0c6836e 100644
--- a/cpu_ref/rsCpuIntrinsic3DLUT.cpp
+++ b/cpu_ref/rsCpuIntrinsic3DLUT.cpp
@@ -18,9 +18,6 @@
 #include "rsCpuIntrinsic.h"
 #include "rsCpuIntrinsicInlines.h"
 
-using namespace android;
-using namespace android::renderscript;
-
 namespace android {
 namespace renderscript {
 
@@ -43,10 +40,6 @@
                        uint32_t outstep);
 };
 
-}
-}
-
-
 void RsdCpuScriptIntrinsic3DLUT::setGlobalObj(uint32_t slot, ObjectBase *data) {
     rsAssert(slot == 0);
     mLUT.set(static_cast<Allocation *>(data));
@@ -179,9 +172,11 @@
     mLUT.clear();
 }
 
-
 RsdCpuScriptImpl * rsdIntrinsic_3DLUT(RsdCpuReferenceImpl *ctx,
                                     const Script *s, const Element *e) {
 
     return new RsdCpuScriptIntrinsic3DLUT(ctx, s, e);
 }
+
+} // namespace renderscript
+} // namespace android