[llvm] Remove "using namespace llvm;" from header files (NFC)

Author: kazutakahirata

llvm/include/llvm/ADT/GenericUniformityImpl.h

@@ -49,8 +49,6 @@
 
 #define DEBUG_TYPE "uniformity"
 
-using namespace llvm;
-
 namespace llvm {
 
 template <typename Range> auto unique(Range &&R) {

llvm/include/llvm/Transforms/IPO/FunctionSpecialization.h

@@ -84,8 +84,6 @@
 #include "llvm/Transforms/Utils/SCCPSolver.h"
 #include "llvm/Transforms/Utils/SizeOpts.h"
 
-using namespace llvm;
-
 namespace llvm {
 // Map of potential specializations for each function. The FunctionSpecializer
 // keeps the discovered specialisation opportunities for the module in a single

llvm/include/llvm/Transforms/Instrumentation/CFGMST.h

@@ -28,8 +28,6 @@
 
 #define DEBUG_TYPE "cfgmst"
 
-using namespace llvm;
-
 namespace llvm {
 
 /// An union-find based Minimum Spanning Tree for CFG