[WebAssembly] clang-tidy (NFC)

Summary:
This patch fixes clang-tidy warnings on wasm-only files.
The list of checks used is:
`-*,clang-diagnostic-*,llvm-*,misc-*,-misc-unused-parameters,readability-identifier-naming,modernize-*`
(LLVM's default .clang-tidy list is the same except it does not have
`modernize-*`. But I've seen in multiple CLs in LLVM the modernize style
was recommended and code was fixed based on the style, so I added it as
well.)

The common fixes are:
- Variable names start with an uppercase letter
- Function names start with a lowercase letter
- Use `auto` when you use casts so the type is evident
- Use inline initialization for class member variables
- Use `= default` for empty constructors / destructors
- Use `using` in place of `typedef`

Reviewers: sbc100, tlively, aardappel

Subscribers: dschuff, sunfish, jgravelle-google, yurydelendik, kripken, MatzeB, mgorny, rupprecht, llvm-commits

Differential Revision: https://reviews.llvm.org/D57500

llvm-svn: 353075
diff --git a/llvm/tools/llvm-objdump/WasmDump.cpp b/llvm/tools/llvm-objdump/WasmDump.cpp
index 1c805ba..45eb8fc 100644
--- a/llvm/tools/llvm-objdump/WasmDump.cpp
+++ b/llvm/tools/llvm-objdump/WasmDump.cpp
@@ -18,7 +18,7 @@
 using namespace object;
 
 void llvm::printWasmFileHeader(const object::ObjectFile *Obj) {
-  const WasmObjectFile *File = dyn_cast<const WasmObjectFile>(Obj);
+  const auto *File = dyn_cast<const WasmObjectFile>(Obj);
 
   outs() << "Program Header:\n";
   outs() << "Version: 0x";