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/Transforms/InstCombine/InstCombine.h b/llvm/lib/Transforms/InstCombine/InstCombine.h
index 247d791..623f25d 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombine.h
+++ b/llvm/lib/Transforms/InstCombine/InstCombine.h
@@ -7,8 +7,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef INSTCOMBINE_INSTCOMBINE_H
-#define INSTCOMBINE_INSTCOMBINE_H
+#ifndef LLVM_LIB_TRANSFORMS_INSTCOMBINE_INSTCOMBINE_H
+#define LLVM_LIB_TRANSFORMS_INSTCOMBINE_INSTCOMBINE_H
 
 #include "InstCombineWorklist.h"
 #include "llvm/Analysis/TargetFolder.h"