[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/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyAsmBackend.cpp b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyAsmBackend.cpp
index 890524d..80c8db4 100644
--- a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyAsmBackend.cpp
+++ b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyAsmBackend.cpp
@@ -35,7 +35,6 @@
 public:
   explicit WebAssemblyAsmBackend(bool Is64Bit)
       : MCAsmBackend(support::little), Is64Bit(Is64Bit) {}
-  ~WebAssemblyAsmBackend() override {}
 
   unsigned getNumFixupKinds() const override {
     return WebAssembly::NumTargetFixupKinds;
@@ -91,7 +90,7 @@
 
 bool WebAssemblyAsmBackend::writeNopData(raw_ostream &OS,
                                          uint64_t Count) const {
-  for (uint64_t i = 0; i < Count; ++i)
+  for (uint64_t I = 0; I < Count; ++I)
     OS << char(WebAssembly::Nop);
 
   return true;
@@ -118,8 +117,8 @@
 
   // For each byte of the fragment that the fixup touches, mask in the
   // bits from the fixup value.
-  for (unsigned i = 0; i != NumBytes; ++i)
-    Data[Offset + i] |= uint8_t((Value >> (i * 8)) & 0xff);
+  for (unsigned I = 0; I != NumBytes; ++I)
+    Data[Offset + I] |= uint8_t((Value >> (I * 8)) & 0xff);
 }
 
 std::unique_ptr<MCObjectTargetWriter>