Clean up assembly statement separator support.

The MC asm lexer wasn't honoring a non-default (anything but ';') statement
separator. Fix that, and generalize a bit to support multi-character
statement separators.

llvm-svn: 128227
diff --git a/llvm/lib/MC/MCAsmInfo.cpp b/llvm/lib/MC/MCAsmInfo.cpp
index 8199fb2..116c007 100644
--- a/llvm/lib/MC/MCAsmInfo.cpp
+++ b/llvm/lib/MC/MCAsmInfo.cpp
@@ -26,7 +26,7 @@
   LinkerRequiresNonEmptyDwarfLines = false;
   MaxInstLength = 4;
   PCSymbol = "$";
-  SeparatorChar = ';';
+  SeparatorString = ";";
   CommentColumn = 40;
   CommentString = "#";
   LabelSuffix = ":";