Fix defaults for preg ini settings

Use the RuntimeOptions, rather than hard-coding them

hphp/runtime/base/preg.cpp

@@ -149,10 +149,12 @@ static __thread int t_last_error_code;
 namespace {
 
 static void preg_init_thread_locals() {
-    IniSetting::Bind("pcre.backtrack_limit", "1000000", ini_on_update_long,
-                     &g_context->m_preg_backtrace_limit);
-    IniSetting::Bind("pcre.recursion_limit", "100000", ini_on_update_long,
-                     &g_context->m_preg_recursion_limit);
+  IniSetting::Bind("pcre.backtrack_limit",
+                   std::to_string(RuntimeOption::PregBacktraceLimit).c_str(),
+                   ini_on_update_long, &g_context->m_preg_backtrace_limit);
+  IniSetting::Bind("pcre.recursion_limit",
+                   std::to_string(RuntimeOption::PregRecursionLimit).c_str(),
+                   ini_on_update_long, &g_context->m_preg_recursion_limit);
 }
 InitFiniNode init(preg_init_thread_locals, InitFiniNode::ThreadInit);