[WebAssembly] replaced .param/.result by .functype

Summary:
This makes it easier/cleaner to generate a single signature from
this directive. Also:
- Adds the symbol name, such that we don't depend on the location
  of this directive anymore.
- Actually constructs the signature in the assembler, and make the
  assembler own it.
- Refactor the use of MVT vs ValType in the streamer and assembler
  to require less conversions overall.
- Changed 700 or so tests to use it.

Reviewers: sbc100, dschuff

Subscribers: jgravelle-google, eraman, aheejin, sunfish, jfb, llvm-commits

Differential Revision: https://reviews.llvm.org/D54652

llvm-svn: 347228
diff --git a/llvm/test/CodeGen/WebAssembly/main-declaration.ll b/llvm/test/CodeGen/WebAssembly/main-declaration.ll
index 8d9414f..f9d68db 100644
--- a/llvm/test/CodeGen/WebAssembly/main-declaration.ll
+++ b/llvm/test/CodeGen/WebAssembly/main-declaration.ll
@@ -14,6 +14,7 @@
 
 ; CHECK-NOT:   __original_main
 ; CHECK-LABEL: foo:
+; CHECK-NEXT:    .functype foo () -> ()
 ; CHECK-NEXT:    call main@FUNCTION
 ; CHECK-NEXT:    end_function
 ; CHECK-NOT:   __original_main