get a definition of strull on windows, thanks to Howard Su.

llvm-svn: 73929
diff --git a/llvm/tools/llvm-mc/AsmLexer.cpp b/llvm/tools/llvm-mc/AsmLexer.cpp
index 0828594..95937d2 100644
--- a/llvm/tools/llvm-mc/AsmLexer.cpp
+++ b/llvm/tools/llvm-mc/AsmLexer.cpp
@@ -14,6 +14,7 @@
 #include "AsmLexer.h"
 #include "llvm/Support/SourceMgr.h"
 #include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Config/config.h"  // for strtoull.
 #include <cerrno>
 #include <cstdio>
 #include <cstdlib>