throw() specs deprecated

Summary: Switch to noexcept

Test Plan: run unit tests

Reviewed By: robbert@fb.com, andrei.alexandrescu@fb.com

Subscribers: aalexandre, sdwilsh, njormrod, folly-diffs@

FB internal diff: D1644135

Tasks: 5486739

Signature: t1:1644135:1414715537:22e1baf91ab7e3250b0b2a460a12d56783f2baed

folly/test/function_benchmark/test_functions.cpp

@@ -25,9 +25,9 @@
 class Exception : public std::exception {
  public:
   explicit Exception(const std::string& value) : value_(value) {}
-  virtual ~Exception(void) throw() {}
+  virtual ~Exception(void) noexcept {}
 
-  virtual const char *what(void) const throw() {
+  virtual const char *what(void) const noexcept {
     return value_.c_str();
   }