Unbreak build with gcc 4.3: provide missed includes and silence most annoying warnings.

llvm-svn: 47367
diff --git a/llvm/lib/AsmParser/LLLexer.cpp b/llvm/lib/AsmParser/LLLexer.cpp
index 7c79c61..f78079b 100644
--- a/llvm/lib/AsmParser/LLLexer.cpp
+++ b/llvm/lib/AsmParser/LLLexer.cpp
@@ -18,6 +18,8 @@
 
 #include <list>
 #include "llvmAsmParser.h"
+
+#include <cstring>
 using namespace llvm;
 
 //===----------------------------------------------------------------------===//