Allocate stacks with guard pages by default

Summary: This was on for mcrouter for very long time. We should make it default for everyone.

Reviewed By: yfeldblum

Differential Revision: D3023133

fb-gh-sync-id: 6401f86df754e9490d46beb5fd9d0cf4b3675208
fbshipit-source-id: 6401f86df754e9490d46beb5fd9d0cf4b3675208

folly/experimental/fibers/FiberManager.h

@@ -104,7 +104,7 @@ class FiberManager : public ::folly::Executor {
     /**
      * Protect limited amount of fiber stacks with guard pages.
      */
-    bool useGuardPages{false};
+    bool useGuardPages{true};
 
     /**
      * Free unnecessary fibers in the fibers pool every fibersPoolResizePeriodMs