[WebAssembly] Implement getRelocationValueString()

And use it in llvm-objdump.

Differential Revision: https://reviews.llvm.org/D46092

llvm-svn: 330957
diff --git a/llvm/test/tools/llvm-objdump/WebAssembly/relocations.test b/llvm/test/tools/llvm-objdump/WebAssembly/relocations.test
index 25628a5..4f4c1b5 100644
--- a/llvm/test/tools/llvm-objdump/WebAssembly/relocations.test
+++ b/llvm/test/tools/llvm-objdump/WebAssembly/relocations.test
@@ -5,4 +5,4 @@
 @bar = hidden global i32* @foo2, align 4
 
 ; CHECK:      RELOCATION RECORDS FOR [DATA]:
-; CHECK-NEXT: 00000018 R_WEBASSEMBLY_MEMORY_ADDR_I32 1+0
+; CHECK-NEXT: 00000018 R_WEBASSEMBLY_MEMORY_ADDR_I32 foo2+0