Minimize uses of lazy initialization by adding explicit initialization functions.

src/platform-posix.h

Index: src/platform-posix.h
diff --git a/src/platform-posix.h b/src/platform-posix.h
index 4ae0e526fb20037e9026a346eeae7d4048207fff..7a982ed2ef3080dad77860d6f46b356a9067bf3b 100644
--- a/src/platform-posix.h
+++ b/src/platform-posix.h
@@ -31,9 +31,8 @@
 namespace v8 {
 namespace internal {
 
-// Used by platform implementation files during OS::PostSetUp() to initialize
-// the math functions.
-void MathSetup();
+// Used by platform implementation files during OS::PostSetUp().
+void POSIXPostSetUp();
 
 } }  // namespace v8::internal