[WebAssembly] Add '.eventtype' directive support

Summary:
This patch supports `.eventtype` directive printing and parsing in the
same syntax with `.functype`.

Reviewers: aardappel, sbc100

Subscribers: dschuff, sbc100, jgravelle-google, sunfish, llvm-commits

Differential Revision: https://reviews.llvm.org/D55353

llvm-svn: 348818
diff --git a/llvm/test/CodeGen/WebAssembly/exception.ll b/llvm/test/CodeGen/WebAssembly/exception.ll
index b53cd0c..b0365fc 100644
--- a/llvm/test/CodeGen/WebAssembly/exception.ll
+++ b/llvm/test/CodeGen/WebAssembly/exception.ll
@@ -262,4 +262,4 @@
 declare %struct.Cleanup* @_ZN7CleanupD1Ev(%struct.Cleanup* returned)
 
 ; CHECK: __cpp_exception:
-; CHECK: .eventtype  __cpp_exception, void, i32
+; CHECK: .eventtype  __cpp_exception i32