ews: switch high_resolution_clock to steady_clock

high_resolution_clock, in practice, is just a typedef to either
system_clock or steady_clock. Be explicit about what we want: for
age, a "stopwatch" is good enough.

[Under GNU stdlibc++ 14, the granularity of system_clock and
steady_clock is the same, and high_resolution_clock is aliased to
system_clock. Under clang libc++ however, system_clock has just a
coarse 1µs granularity vs. steady_clock's 1ns, and
high_resolution_clock is aliased to steady_clock.]

exch/ews/context.cpp

@@ -325,12 +325,9 @@ void Cleaner::operator()(MESSAGE_CONTENT *x) {message_content_free(x);}
 
 EWSContext::EWSContext(int id, HTTP_AUTH_INFO ai, const char *data, uint64_t length,
     EWSPlugin &p) :
-	m_ID(id),
-	m_orig(*get_request(id)),
-	m_auth_info(ai),
-	m_request(data, length),
-	m_response(p.server_version()),
-	m_plugin(p)
+	m_ID(id), m_orig(*get_request(id)), m_auth_info(ai),
+	m_request(data, length), m_response(p.server_version()), m_plugin(p),
+	m_created(tp_now())
 {
 	tinyxml2::XMLElement* imp = nullptr;
 	if(m_request.header && (imp = m_request.header->FirstChildElement("ExchangeImpersonation")) &&
@@ -346,7 +343,9 @@ EWSContext::~EWSContext()
 }
 
 double EWSContext::age() const
-{return std::chrono::duration<double>(std::chrono::high_resolution_clock::now()-m_created).count();}
+{
+	return std::chrono::duration<double>(tp_now() - m_created).count();
+}
 
 /**
  * @brief      Copy string to context allocated buffer

exch/ews/ews.cpp

@@ -143,8 +143,8 @@ struct EWSPlugin::DebugCtx
 	std::mutex requestLock{};
 	std::mutex hashLock{};
 	std::unordered_map<uint64_t, size_t> requestHashes; ///< How often a request with this hash value occurred
-	std::chrono::high_resolution_clock::time_point last;
-	std::chrono::high_resolution_clock::duration minRequestTime{};
+	gromox::time_point last{};
+	gromox::time_duration minRequestTime{};
 	uint32_t loopThreshold = 0;  ///< How many request repetitions to ignore before warning
 	uint8_t flags = 0;
 };
@@ -334,7 +334,7 @@ http_status EWSPlugin::dispatch(int ctx_id, HTTP_AUTH_INFO& auth_info, const voi
 			lockProxy = std::unique_lock<std::mutex>(debug->requestLock);
 		if(debug->flags & DebugCtx::FL_RATELIMIT)
 		{
-			auto now = std::chrono::high_resolution_clock::now();
+			auto now = tp_now();
 			std::this_thread::sleep_for(debug->last-now+debug->minRequestTime);
 			debug->last = now;
 		}

exch/ews/ews.hpp

@@ -374,7 +374,7 @@ class EWSContext {
 	EWSPlugin& m_plugin;
 	std::string impersonationUser; ///< Buffer to hold username of impersonated user
 	std::string impersonationMaildir; ///< Buffer to hold maildir of impersonated user
-	std::chrono::high_resolution_clock::time_point m_created = std::chrono::high_resolution_clock::now();
+	gromox::time_point m_created{};
 	std::unique_ptr<NotificationContext> m_notify;
 };