[MC] Fix some Clang-tidy modernize and Include What You Use warnings; other minor fixes (NFC).

llvm-svn: 294685
diff --git a/llvm/lib/MC/MCParser/MCTargetAsmParser.cpp b/llvm/lib/MC/MCParser/MCTargetAsmParser.cpp
index 14a22c6..5f82144 100644
--- a/llvm/lib/MC/MCParser/MCTargetAsmParser.cpp
+++ b/llvm/lib/MC/MCParser/MCTargetAsmParser.cpp
@@ -1,4 +1,4 @@
-//===-- MCTargetAsmParser.cpp - Target Assembly Parser ---------------------==//
+//===-- MCTargetAsmParser.cpp - Target Assembly Parser --------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -7,19 +7,16 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/MCParser/MCTargetAsmParser.h"
 #include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCParser/MCTargetAsmParser.h"
+
 using namespace llvm;
 
 MCTargetAsmParser::MCTargetAsmParser(MCTargetOptions const &MCOptions,
                                      const MCSubtargetInfo &STI)
-  : AvailableFeatures(0), ParsingInlineAsm(false), MCOptions(MCOptions),
-    STI(&STI)
-{
-}
+  : MCOptions(MCOptions), STI(&STI) {}
 
-MCTargetAsmParser::~MCTargetAsmParser() {
-}
+MCTargetAsmParser::~MCTargetAsmParser() = default;
 
 MCSubtargetInfo &MCTargetAsmParser::copySTI() {
   MCSubtargetInfo &STICopy = getContext().getSubtargetCopy(getSTI());