[libFuzzer] Clean up headers and file formatting of LibFuzzer files.

Reorganize #includes to follow LLVM Coding Standards.
Include some missing headers. Required to use `Printf()`.

Aside from that, this patch contains no functional change.
It is purely a re-organization.

Differential Revision: https://reviews.llvm.org/D27363

llvm-svn: 289560
diff --git a/llvm/lib/Fuzzer/FuzzerIO.cpp b/llvm/lib/Fuzzer/FuzzerIO.cpp
index 5d4d415..eda8e87 100644
--- a/llvm/lib/Fuzzer/FuzzerIO.cpp
+++ b/llvm/lib/Fuzzer/FuzzerIO.cpp
@@ -8,6 +8,7 @@
 //===----------------------------------------------------------------------===//
 // IO functions.
 //===----------------------------------------------------------------------===//
+
 #include "FuzzerIO.h"
 #include "FuzzerDefs.h"
 #include "FuzzerExtFunctions.h"
@@ -15,8 +16,8 @@
 #include <cstdarg>
 #include <fstream>
 #include <iterator>
-#include <sys/types.h>
 #include <sys/stat.h>
+#include <sys/types.h>
 
 namespace fuzzer {