Canonicalize header guards into a common format.

Add header guards to files that were missing guards. Remove #endif comments
as they don't seem common in LLVM (we can easily add them back if we decide
they're useful)

Changes made by clang-tidy with minor tweaks.

llvm-svn: 215558
diff --git a/llvm/lib/MC/MCDisassembler/Disassembler.h b/llvm/lib/MC/MCDisassembler/Disassembler.h
index d1d40cd..46d0c4c 100644
--- a/llvm/lib/MC/MCDisassembler/Disassembler.h
+++ b/llvm/lib/MC/MCDisassembler/Disassembler.h
@@ -14,8 +14,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef LLVM_MC_DISASSEMBLER_H
-#define LLVM_MC_DISASSEMBLER_H
+#ifndef LLVM_LIB_MC_MCDISASSEMBLER_DISASSEMBLER_H
+#define LLVM_LIB_MC_MCDISASSEMBLER_DISASSEMBLER_H
 
 #include "llvm-c/Disassembler.h"
 #include "llvm/ADT/SmallString.h"