[WebAssembly] Create a TargetInfo header.  NFC

Move the declarations of getThe<Name>Target() functions into a new header in
TargetInfo and make users of these functions include this new header.
This fixes a layering problem.

llvm-svn: 360735
diff --git a/llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp b/llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp
index 9d5bb3f..44136b69 100644
--- a/llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp
+++ b/llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp
@@ -15,6 +15,7 @@
 
 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
 #include "MCTargetDesc/WebAssemblyTargetStreamer.h"
+#include "TargetInfo/WebAssemblyTargetInfo.h"
 #include "WebAssembly.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCExpr.h"