Fix violations of [basic.class.scope]p2.

These cases all follow the same pattern:

struct A {
  friend class X;
  //...
  class X {};
};

But 'friend class X;' injects 'X' into the surrounding namespace scope,
rather than introducing a class member. So the second 'class X {}' is a
completely different type, which changes the meaning of the earlier name
'X' from '::X' to 'A::X'.

Additionally, the friend declaration is pointless -- members of a class
don't need to be befriended to be able to access private members.

clang/lib/Analysis/CFG.cpp

@@ -223,8 +223,6 @@ class AddStmtChoice {
 ///
 class LocalScope {
 public:
-  friend class const_iterator;
-
   using AutomaticVarsTy = BumpVector<VarDecl *>;
 
   /// const_iterator - Iterates local scope backwards and jumps to previous

clang/utils/TableGen/NeonEmitter.cpp

@@ -303,8 +303,6 @@ class Variable {
 /// The main grunt class. This represents an instantiation of an intrinsic with
 /// a particular typespec and prototype.
 class Intrinsic {
-  friend class DagEmitter;
-
   /// The Record this intrinsic was created from.
   Record *R;
   /// The unmangled name.

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h

@@ -640,7 +640,6 @@ class DwarfDebug : public DebugHandlerBase {
   void addDwarfTypeUnitType(DwarfCompileUnit &CU, StringRef Identifier,
                             DIE &Die, const DICompositeType *CTy);
 
-  friend class NonTypeUnitContext;
   class NonTypeUnitContext {
     DwarfDebug *DD;
     decltype(DwarfDebug::TypeUnitsUnderConstruction) TypeUnitsUnderConstruction;

llvm/lib/CodeGen/InterferenceCache.h

@@ -157,8 +157,6 @@ class LLVM_LIBRARY_VISIBILITY InterferenceCache {
   Entry *get(unsigned PhysReg);
 
 public:
-  friend class Cursor;
-
   InterferenceCache() = default;
 
   ~InterferenceCache() {