Don't duplicate OS::ActivationFrameAlignment() for every POSIX platform.

src/platform-solaris.cc

Index: src/platform-solaris.cc
diff --git a/src/platform-solaris.cc b/src/platform-solaris.cc
index 46fff60e191466e72d0cb6e899556841ef58bf01..b1d88af2939de69b8a4fc31a18786318a24af346 100644
--- a/src/platform-solaris.cc
+++ b/src/platform-solaris.cc
@@ -84,12 +84,6 @@ namespace internal {
 static Mutex* limit_mutex = NULL;
 
 
-int OS::ActivationFrameAlignment() {
-  // GCC generates code that requires 16 byte alignment such as movdqa.
-  return Max(STACK_ALIGN, 16);
-}
-
-
 const char* OS::LocalTimezone(double time) {
   if (std::isnan(time)) return "";
   time_t tv = static_cast<time_t>(floor(time/msPerSecond));