[WebAssembly] Remove "name" section of object wasm object files

LLD is unaffected, no changes needed there. LLD continues to
write out a name section, using the symbol names.

Fixes: https://github.com/WebAssembly/tool-conventions/issues/37

Patch by Nicholas Wilson!

Differential Revision: https://reviews.llvm.org/D42425

llvm-svn: 323234