Fix build on FreeBSD

The build was failing with the following message:

```
../src/profiler/sampler.cc:216:10: error: static_cast from 'pthread_t' (aka 'pthread *') to 'uint32_t' (aka 'unsigned int') is not allowed
  return static_cast<uint32_t>(thread_id);
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
```

It seems that using the reinterpret_cast function as in OSX fixes the
issue.

Author: ignisf

patches/0001-Build-a-standalone-static-library.patch

@@ -1,7 +1,7 @@
-From 9aa7780d5c7434706ba12b81ab021e0db9850982 Mon Sep 17 00:00:00 2001
+From 84470a0b6c696f42aa7f86ba5ffd22b17e0047c4 Mon Sep 17 00:00:00 2001
 From: Petko Bordjukov <[email protected]>
 Date: Mon, 25 Jul 2016 00:00:19 +0300
-Subject: [PATCH 1/3] Build a standalone static library
+Subject: [PATCH 1/4] Build a standalone static library
 
 ---
  gypfiles/standalone.gypi | 3 +++

patches/0002-Don-t-compile-unnecessary-stuff.patch

@@ -1,7 +1,7 @@
-From bb7beaa8dddf7d406de80cc6511abe942dfeabd6 Mon Sep 17 00:00:00 2001
+From 930d596106fb3289f6aa37cdf8abaec3106c31b9 Mon Sep 17 00:00:00 2001
 From: Petko Bordjukov <[email protected]>
 Date: Mon, 25 Jul 2016 00:04:07 +0300
-Subject: [PATCH 2/3] Don't compile unnecessary stuff
+Subject: [PATCH 2/4] Don't compile unnecessary stuff
 
 ---
  Makefile         |  7 +------

patches/0003-Use-the-fPIC-flag-for-the-static-library.patch

@@ -1,7 +1,7 @@
-From 22cd3f03af2d94da1f7506a8daa7708e8c93b928 Mon Sep 17 00:00:00 2001
+From 8873d0ee6e1304e256bf3181b287e189bc68a9c8 Mon Sep 17 00:00:00 2001
 From: Petko Bordjukov <[email protected]>
 Date: Mon, 25 Jul 2016 00:05:47 +0300
-Subject: [PATCH 3/3] Use the -fPIC flag for the static library
+Subject: [PATCH 3/4] Use the -fPIC flag for the static library
 
 ---
  gypfiles/standalone.gypi | 2 +-

patches/0004-Reinterpret-thread-hash-for-FreeBSD-too.patch

@@ -0,0 +1,25 @@
+From 0f376ac8f77980b86bfbfb55e3a1714201a0f78f Mon Sep 17 00:00:00 2001
+From: Petko Bordjukov <[email protected]>
+Date: Wed, 27 Jul 2016 06:20:13 +0300
+Subject: [PATCH 4/4] Reinterpret thread hash for FreeBSD, too
+
+---
+ src/profiler/sampler.cc | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/src/profiler/sampler.cc b/src/profiler/sampler.cc
+index ae47dca..4eb8780 100644
+--- a/src/profiler/sampler.cc
++++ b/src/profiler/sampler.cc
+@@ -210,7 +210,7 @@ void* ThreadKey(pthread_t thread_id) {
+ 
+ // Returns hash value for hash map.
+ uint32_t ThreadHash(pthread_t thread_id) {
+-#if V8_OS_MACOSX
++#if (V8_OS_MACOSX || V8_OS_FREEBSD)
+   return static_cast<uint32_t>(reinterpret_cast<intptr_t>(thread_id));
+ #else
+   return static_cast<uint32_t>(thread_id);
+-- 
+2.9.0
+