[ms-inline asm] Add a new Inline Asm Non-Standard Dialect attribute.

This new attribute is intended to be used by the backend to determine how
the inline asm string should be parsed/printed. This patch adds the 
ia_nsdialect attribute and also adds a test case to ensure the IR is
correctly parsed, but there is no functional change at this time.

The standard dialect is assumed to be AT&T.  Therefore, this attribute
should only be added to MS-style inline assembly statements, which use
the Intel dialect.  If we ever support more dialects we'll need to
add additional state to the attribute.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161641 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AsmParser/LLParser.cpp b/lib/AsmParser/LLParser.cpp
index 095b7c5..0ff8edd 100644
--- a/lib/AsmParser/LLParser.cpp
+++ b/lib/AsmParser/LLParser.cpp
@@ -962,6 +962,7 @@
     case lltok::kw_naked:           Attrs |= Attribute::Naked; break;
     case lltok::kw_nonlazybind:     Attrs |= Attribute::NonLazyBind; break;
     case lltok::kw_address_safety:  Attrs |= Attribute::AddressSafety; break;
+    case lltok::kw_ia_nsdialect:    Attrs |= Attribute::IANSDialect; break;
 
     case lltok::kw_alignstack: {
       unsigned Alignment;