clean-up libutils includes

moved Foo.h as first include of Foo.cpp, and
removed redundant includes.

Made NativeHandle non virtual.


Test: run & compile
Bug: n/a

Change-Id: I37fa746cd42c9ba23aba181f84cb6c619386406a
diff --git a/libutils/ProcessCallStack.cpp b/libutils/ProcessCallStack.cpp
index 73ed4eb..1d9f30d 100644
--- a/libutils/ProcessCallStack.cpp
+++ b/libutils/ProcessCallStack.cpp
@@ -17,18 +17,11 @@
 #define LOG_TAG "ProcessCallStack"
 // #define LOG_NDEBUG 0
 
-#include <dirent.h>
-#include <errno.h>
-#include <stdio.h>
-#include <string.h>
-#include <memory>
-
-#include <utils/Log.h>
-#include <utils/Errors.h>
 #include <utils/ProcessCallStack.h>
-#include <utils/Printer.h>
 
-#include <limits.h>
+#include <dirent.h>
+
+#include <utils/Printer.h>
 
 namespace android {