[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/FuzzerUtilWindows.cpp b/llvm/lib/Fuzzer/FuzzerUtilWindows.cpp
index 91509cc..fea09a6 100644
--- a/llvm/lib/Fuzzer/FuzzerUtilWindows.cpp
+++ b/llvm/lib/Fuzzer/FuzzerUtilWindows.cpp
@@ -8,7 +8,6 @@
 //===----------------------------------------------------------------------===//
 // Misc utils implementation for Windows.
 //===----------------------------------------------------------------------===//
-
 #include "FuzzerDefs.h"
 #if LIBFUZZER_WINDOWS
 #include "FuzzerIO.h"
@@ -179,4 +178,5 @@
 }
 
 } // namespace fuzzer
+
 #endif // LIBFUZZER_WINDOWS