Fix unsafe cast in RegExpStack

src/regexp-stack.h

Index: src/regexp-stack.h
diff --git a/src/regexp-stack.h b/src/regexp-stack.h
index eb6df6a92d0fd0a2fc50de4a39fff964abd6b576..99cf33cd325cbeb6f98663539645a6d915eb4061 100644
--- a/src/regexp-stack.h
+++ b/src/regexp-stack.h
@@ -74,7 +74,7 @@ class RegExpStack {
 
  private:
   // Artificial limit used when no memory has been allocated.
-  static const uintptr_t kMemoryTop = -1;
+  static const uintptr_t kMemoryTop = static_cast<uintptr_t>(-1);
 
   // Minimal size of allocated stack area.
   static const size_t kMinimumStackSize = 1 * KB;