[clang][ASTReader] Fix memory leak while reading FriendTemplateDecls

[kadircet]

Summary

Allocate on ASTContext, rather than just on heap, so that template
parameter lists are freed up.

clang/lib/Serialization/ASTReaderDecl.cpp

void ASTDeclReader::VisitFriendDecl(FriendDecl *D) {
   D->UnsupportedFriend = (Record.readInt() != 0);
   D->FriendLoc = readSourceLocation();
 }
 
 void ASTDeclReader::VisitFriendTemplateDecl(FriendTemplateDecl *D) {
   VisitDecl(D);
   unsigned NumParams = Record.readInt();
   D->NumParams = NumParams;
-  D->Params = new TemplateParameterList*[NumParams];
+  D->Params = new (Reader.getContext()) TemplateParameterList *[NumParams];
   for (unsigned i = 0; i != NumParams; ++i)
     D->Params[i] = Record.readTemplateParameterList();
   if (Record.readInt()) // HasFriendDecl
     D->Friend = readDeclAs<NamedDecl>();
   else
     D->Friend = readTypeSourceInfo();
   D->FriendLoc = readSourceLocation();
 }