[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/docs/LangRef.html b/docs/LangRef.html
index ef58b98..0ea83dd 100644
--- a/docs/LangRef.html
+++ b/docs/LangRef.html
@@ -1208,6 +1208,13 @@
       may make calls to the function faster, at the cost of extra program
       startup time if the function is not called during program startup.</dd>
 
+  <dt><tt><b>ia_nsdialect</b></tt></dt>
+  <dd>This attribute indicates the associated inline assembly call is using a
+      non-standard assembly dialect.  The standard dialect is ATT, which is
+      assumed when this attribute is not present.  When present, the dialect
+      is assumed to be Intel.  Currently, ATT and Intel are the only supported
+      dialects.</dd>
+
   <dt><tt><b>inlinehint</b></tt></dt>
   <dd>This attribute indicates that the source code contained a hint that inlining
       this function is desirable (such as the "inline" keyword in C/C++).  It