Update V8 to r3431 as required by WebKit r51976.

Change-Id: I567392c3f8c0a0d5201a4249611ac4ccf468cd5b
diff --git a/SConstruct b/SConstruct
index 2b2ce1d..2087a94 100755
--- a/SConstruct
+++ b/SConstruct
@@ -149,6 +149,11 @@
       'LIBPATH' : ['/usr/local/lib'],
       'CCFLAGS':      ['-ansi'],
     },
+    'os:openbsd': {
+      'CPPPATH' : ['/usr/local/include'],
+      'LIBPATH' : ['/usr/local/lib'],
+      'CCFLAGS':      ['-ansi'],
+    },
     'os:win32': {
       'CCFLAGS':      ['-DWIN32'],
       'CXXFLAGS':     ['-DWIN32'],
@@ -273,7 +278,7 @@
       'WARNINGFLAGS': ['/W3']
     },
     'arch:x64': {
-      'WARNINGFLAGS': ['/W2']
+      'WARNINGFLAGS': ['/W3']
     },
     'arch:arm': {
       'CPPDEFINES':   ['V8_TARGET_ARCH_ARM'],
@@ -299,6 +304,9 @@
     'os:freebsd': {
       'LIBS': ['execinfo', 'pthread']
     },
+    'os:openbsd': {
+      'LIBS': ['execinfo', 'pthread']
+    },
     'os:win32': {
       'LIBS': ['winmm', 'ws2_32'],
     },
@@ -345,6 +353,9 @@
     'os:freebsd': {
       'LIBS':         ['execinfo', 'pthread']
     },
+    'os:openbsd': {
+      'LIBS':         ['execinfo', 'pthread']
+    },
     'os:win32': {
       'LIBS': ['winmm', 'ws2_32']
     },
@@ -398,7 +409,11 @@
     },
     'os:freebsd': {
       'LIBPATH' : ['/usr/local/lib'],
-      'LIBS':         ['execinfo', 'pthread']
+      'LIBS':     ['execinfo', 'pthread']
+    },
+    'os:openbsd': {
+      'LIBPATH' : ['/usr/local/lib'],
+      'LIBS':     ['execinfo', 'pthread']
     },
     'os:win32': {
       'LIBS':         ['winmm', 'ws2_32']
@@ -505,6 +520,9 @@
     'os:freebsd': {
       'LIBS': ['pthread'],
     },
+    'os:openbsd': {
+      'LIBS': ['pthread'],
+    },
     'os:android': {
       'LIBPATH':     [ANDROID_TOP + '/out/target/product/generic/obj/lib'],
       'LINKFLAGS':    ANDROID_LINKFLAGS,
@@ -555,7 +573,7 @@
     'help': 'the toolchain to use (' + TOOLCHAIN_GUESS + ')'
   },
   'os': {
-    'values': ['freebsd', 'linux', 'macos', 'win32', 'android'],
+    'values': ['freebsd', 'linux', 'macos', 'win32', 'android', 'openbsd'],
     'default': OS_GUESS,
     'help': 'the os to build for (' + OS_GUESS + ')'
   },