nghttpx: Use constexpr

src/shrpx_connection.cc

@@ -561,7 +561,7 @@ int Connection::check_http2_requirement() {
 }
 
 namespace {
-const size_t SHRPX_SMALL_WRITE_LIMIT = 1300;
+constexpr size_t SHRPX_SMALL_WRITE_LIMIT = 1300;
 } // namespace
 
 size_t Connection::get_tls_write_limit() {

src/shrpx_http2_session.cc

@@ -54,8 +54,8 @@ using namespace nghttp2;
 namespace shrpx {
 
 namespace {
-const ev_tstamp CONNCHK_TIMEOUT = 5.;
-const ev_tstamp CONNCHK_PING_TIMEOUT = 1.;
+constexpr ev_tstamp CONNCHK_TIMEOUT = 5.;
+constexpr ev_tstamp CONNCHK_PING_TIMEOUT = 1.;
 } // namespace
 
 namespace {