Pacify -Wnon-virtual-dtor.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@166270 91177308-0d34-0410-b5e6-96231b3b80d8

lib/MC/MCParser/AsmParser.cpp

@@ -46,6 +46,8 @@ static cl::opt<bool>
 FatalAssemblerWarnings("fatal-assembler-warnings",
                        cl::desc("Consider warnings as error"));
 
+MCAsmParserSemaCallback::~MCAsmParserSemaCallback() {} 
+
 namespace {
 
 /// \brief Helper class for tracking macro definitions.