[WebAssembly] Fix list of relocations with addends in lld

Summary:
The list of relocations with addend in lld was missing `R_WASM_MEMORY_ADDR_REL_SLEB`,
causing `wasm-ld` to generate corrupted output. This fixes that problem and while
we're at it pulls the list of such relocations into the Wasm.h header, to avoid
duplicating it in multiple places.

Reviewers: sbc100
Differential Revision: https://reviews.llvm.org/D63696

llvm-svn: 364367
diff --git a/llvm/lib/MC/WasmObjectWriter.cpp b/llvm/lib/MC/WasmObjectWriter.cpp
index dab5bb3..8743eb7 100644
--- a/llvm/lib/MC/WasmObjectWriter.cpp
+++ b/llvm/lib/MC/WasmObjectWriter.cpp
@@ -147,19 +147,7 @@
       : Offset(Offset), Symbol(Symbol), Addend(Addend), Type(Type),
         FixupSection(FixupSection) {}
 
-  bool hasAddend() const {
-    switch (Type) {
-    case wasm::R_WASM_MEMORY_ADDR_LEB:
-    case wasm::R_WASM_MEMORY_ADDR_SLEB:
-    case wasm::R_WASM_MEMORY_ADDR_REL_SLEB:
-    case wasm::R_WASM_MEMORY_ADDR_I32:
-    case wasm::R_WASM_FUNCTION_OFFSET_I32:
-    case wasm::R_WASM_SECTION_OFFSET_I32:
-      return true;
-    default:
-      return false;
-    }
-  }
+  bool hasAddend() const { return wasm::relocTypeHasAddend(Type); }
 
   void print(raw_ostream &Out) const {
     Out << wasm::relocTypetoString(Type) << " Off=" << Offset