Check for "multipart/" prefix

...instead of full-string compare; regression introduced with
c4927a1b "ByteString->rtl::OString[Buffer]"
erroneously replacing a call to ByteString::CompareIgnoreCaseToAscii(s,n) with a
call to OString::equalsIgnoreAsciiCase(s,n).

Change-Id: I473e3403910e22e43d7350afa88f9a8e103ebf1d

tools/source/inet/inetmsg.cxx

@@ -843,7 +843,7 @@ bool INetMIMEMessage::EnableAttachChild (INetMessageContainerType eType)
     }
 
     // Setup boundary for multipart types.
-    if (aContentType.toString().equalsIgnoreAsciiCase("multipart/"))
+    if (aContentType.toString().startsWithIgnoreAsciiCase("multipart/"))
     {
         // Generate a unique boundary from current time.
         sal_Char sTail[16 + 1];